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15 January 2026

12 Pages

6 H Hydrothermal Synthesis of W-Doped VO2(M) for Smart Windows in Tropical Climates

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1
Escuela de Física, Instituto Tecnológico de Costa Rica, Cartago 159-7050, Costa Rica
2
Centro de Investigación en Ciencia e Ingeniería de Materiales (CICIMA), Universidad de Costa Rica, San Pedro 11501-2060, Costa Rica
3
Programa de Maestría Ingeniería en Dispositivos Médicos, Instituto Tecnológico de Costa Rica, Cartago 159-7050, Costa Rica
4
Escuela de Química, Instituto Tecnológico de Costa Rica, Cartago 159-7050, Costa Rica
Materials2026, 19(2), 345;https://doi.org/10.3390/ma19020345
This article belongs to the Section Metals and Alloys
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Highlights

What are the main findings?
  • Rapid 6 h hydrothermal synthesis of VO2(M)
  • pH ≈ 8.5 enables phase stabilization
  • W-doping lowers Tc by ~17 °C per wt.%
  • Crystallites below 35 nm without annealing
  • Powders suitable for dispersion processing
What are the implications of the main findings?
  • Enables low-cost thermochromic coatings
  • Scalable route for smart-window materials
  • Facilitates integration into polymer films

Abstract

Thermochromic smart windows are a promising technology to reduce energy consumption in buildings, particularly in tropical regions where cooling demands are high. Vanadium dioxide (VO2) is the most studied thermochromic material due to its reversible semiconductor-to-metal transition near 68 °C. Conventional synthesis routes require long reaction times and post-annealing steps. In this work, we report a rapid hydrothermal synthesis of monoclinic VO2(M) and tungsten-doped VO2(M) powders obtained within only 6 h at 270 °C, using vanadyl sulfate as precursor and controlled precipitation at pH ≈ 8.5. Differential scanning calorimetry confirmed the reversible transition at 59 °C for the undoped VO2, with a hysteresis of 18 °C, while tungsten doping reduced the transition temperature by ~17 °C per wt.% of W. X-ray diffraction verified the monoclinic phase with minor traces of VO2(B), a non-thermochromic polymorph of VO2, and microstructural analysis revealed crystallite sizes below 35 nm. Electron microscopy and dynamic light scattering confirmed particle sizes suitable for dispersion in polymeric matrices. This approach significantly reduces synthesis time compared to typical hydrothermal methods requiring 20–48 h and avoids further annealing. The resulting powders provide a low-cost and scalable route for fabricating thermochromic coatings with transition temperatures closer to ambient conditions, making them relevant for smart-window applications in tropical climates, where lower transition temperatures are generally regarded as beneficial.

1. Introduction

Thermochromic smart coatings have gained increasing attention as a strategy to improve the energy performance of buildings [1,2]. Among building components, windows represent one of the main sources of energy loss, as they simultaneously permit heat gain and heat dissipation [3,4]. Thermochromic smart windows address this limitation by dynamically regulating near-infrared radiation. Their optical response changes from a transparent to a reflective state as the ambient temperature increases, without the need for external stimuli, thereby contributing to reduced energy consumption [2,5].
Vanadium dioxide (VO2) is regarded as one of the most extensively investigated thermochromic material [6,7]. It has been incorporated into a wide range of architectures, including thin films [8,9], nanocomposites [10], micro-composites, and advanced engineered structures such as grids or biomimetic designs [11]. VO2 undergoes a reversible first-order phase transition from a monoclinic semiconducting phase (M) to a metallic rutile-type tetragonal phase (R) when the temperature reaches approximately 68 °C [12,13]. This transition is accompanied by a pronounced decrease in electrical resistivity and a substantial increase in infrared reflectance, while the optical response in the visible range remains only weakly affected [14] Although several crystalline phases of VO2 have been reported, only the M and R phases exhibit a fully reversible semiconductor–metal transition [15].
One effective strategy to shift the transition temperature toward ambient conditions is the incorporation of dopants into the VO2 lattice. In particular, tungsten (W) doping has been shown to produce one of the strongest reductions in the transition temperature, with experimentally reported rates of approximately 20–26 °C per wt.% [16]. This tunability is especially relevant for applications in thermochromic windows operating under warm climatic conditions.
Hydrothermal synthesis is widely employed for the preparation of metal oxides and is based on chemical reactions occurring in aqueous environments under elevated temperature and pressure. This approach is commonly used for the synthesis of VO2 nanoparticles [17,18,19], typically requiring temperatures close to 240 °C [20] and reaction times ranging from 20 to 48 h [20,21]. Owing to the multiple stable oxidation states of vanadium, achieving phase-pure VO2 remains challenging. Key parameters such as temperature, reaction time, pressure, precursor feeding rate, reducing agents, and solution chemistry must be carefully controlled to avoid the formation of undesired vanadium oxide phases [7,22,23].
Previous studies report that vanadium oxides can be obtained via hydrothermal routes through different mechanisms, including the reduction in pentavalent vanadium precursors (e.g., V2O5 or NH4VO3) [24,25] using reducing agents, as well as homogeneous precipitation starting from VOSO4 under relatively mild hydrothermal conditions [26]. In recent years, one-step hydrothermal synthesis of monoclinic VO2(M) powders has attracted growing interest, as it eliminates the need for a secondary heat-treatment step and helps suppress particle aggregation and excessive grain growth [27].
Tropical regions are characterized by high ambient temperatures throughout the year, which are further increasing as a consequence of climate change [28,29]. Experimental and simulation studies on thermochromic windows designed for hot climates indicate that these systems can effectively reduce energy loads even in architectural elements such as skylights and sunroofs [30]. Furthermore, it has been demonstrated that lowering the phase transition temperature toward room temperature leads to enhanced energy savings in warm climates compared to regions dominated by cold weather conditions [14,31,32,33].
In this work, we report a rapid one-step hydrothermal precipitation route for the synthesis of doped and undoped VO2(M) particles, achieved within 6 h and without the need for post-annealing treatments. The resulting materials are suitable for integration into thermochromic smart-window systems, where they can contribute to reduced energy consumption by selectively modulating infrared radiation while preserving visible light transmission, which is essential for indoor comfort and human well-being.

2. Materials and Methods

2.1. Synthesis

Vanadium(IV) oxysulfate (VOSO4), ammonium paratungsten ((NH4)10W12O41·5H2O), ammonia (NH3), and xylene were purchased from Sigma-Aldrich (San José, Costa Rica). All the reagents used were ACS grade. Deionized water was used in all the sample preparations.
The synthesis is based on a hydrothermal-assisted homogeneous precipitation approach [19], using the inexpensive and low-toxic VOSO4 as a raw material to produce VO2(M) phase. The reported W concentrations correspond to nominal wt.% values introduced during synthesis. For the synthesis, 1.00 g of VOSO4 was dissolved in 30 mL of deionized water. Tungsten-doped samples were prepared by adding 14.6 or 29.2 mg of (NH4)10W12O41·5H2O, corresponding to nominal W contents of 0.5 and 1.0 wt.%, respectively, while an undoped sample was prepared as a reference. Apart from the initial precursor composition, all samples were synthesized following the same procedure.
The formed dispersion was continuously stirred at a temperature of 60 °C under argon bubbling until a translucent blue solution with a pH value of approximately 2.5 was obtained. Subsequently, an aqueous ammonia solution (NH3, 23%) was added dropwise until the pH reached 8.5 (approximately 2.5 mL), leading to the formation of a pink–grayish precipitate. Temperature and stirring were maintained throughout the precipitation process. The precipitate was collected by centrifugation and washed three times with deionized water, discarding the supernatant after each cycle.
After washing, the precipitate was transferred to a custom madeTeflon liner containing 20 mL of deionized water. The Teflon container (nominal volume 30 mL) was purged with argon prior to sealing and subsequently placed inside a stainless-steel autoclave. The hydrothermal treatment was carried out at 270 °C for 6 h. The external furnace used did not operate under controlled atmosphere. After completion of the reaction, the autoclave was allowed to cool naturally to room temperature by heat exchange with the ambient environment.
The resulting black powder was recovered by centrifugation, washed with deionized water, and dried under a mechanical vacuum at 60 °C for 8 h. The schematic synthesis procedure is shown in Figure 1.
Figure 1. Schematic representation of the hydrothermal-assisted homogeneous precipitation route used for the synthesis of undoped and W-doped VO2(M) powders. Vanadium(IV) oxysulfate (VOSO4) and ammonium paratungstate (NH4)10W12O41·5H2O are dissolved in water under stirring and inert atmosphere, followed by dropwise addition of ammonia (NH3) to induce precipitation. The precipitate is collected, washed, and transferred to a Teflon® liner, sealed in a stainless-steel autoclave, and hydrothermally treated at 270 °C for 6 h to obtain VO2(M). Arrows indicate the sequence of the synthesis steps. The parameter X corresponds to the amount of ammonium paratungstate added (X = 0, 14.6 mg, or 29.2 mg), yielding undoped, 0.5 wt.% W-doped, and 1.0 wt.% W-doped samples, respectively.

2.2. Characterization

2.2.1. Thermal Characterization

The thermal characterization was carried using a DSC250 (TA Instruments, New Castle, DE, USA), using a heating and cooling rate of 10 °C min−1 in inert atmosphere with a flow rate of 50 mL min−1 of nitrogen (UHP) (Praxair, San José, Costa Rica), in a temperature range from 0 to 100 °C. The reversible first-order phase transition was measured by extrapolations of the baselines to a selected temperature range at which the sharp enthalpy signal was detected. The thermogravimetric study (TG) of the samples was conducted on a SDT-600 thermal analyzer (TA Instruments, New Castle, DE, USA) under dry air (Praxair, San José, Costa Rica) flow in the range of −50–550 °C, with a heating rate of 10 °C min−1.

2.2.2. Electron Microscopy

The samples were collected on a metal grid for transmission electron microscopy (TEM) observation. The images were obtained in a TEM (JEM-2011, Jeol Tokyo, Japan) at 200 kV. The samples were analyzed using a scanning electron microscopy SEM Cube-II (EM-Crafts, Hanam, Korea), at 10 kV. EDS mapping was performed using a Xplore 30 mm (Oxford Instruments, Abingdon, UK) and the images were analyzed using the AZtec software (version 6.0, Oxford Instruments).

2.2.3. Dynamic Light Scattering (DLS)

The hydrodynamic diameter of the dispersions was measured using a Nano ZS Zetasizer instrument (Malvern Panalytical Ltd., Worcester, UK). All measurements were performed at 25 °C at 173° angle in xylene, after high-power ultrasound treatment of the samples using a Sonifier QSonica (Ultrasonic Corporation, Newtown, CT, USA).

2.2.4. X-Ray Diffraction (XRD)

X-ray diffraction was carried out in a diffractometer EMPYREAN (Malvern Panalytical Ltd., Worcester, UK). All the analyses were performed using a Cu K-alpha: 1.54060 Å source, 45 kV. Results were compared to a database using the software Highscore Plus 3.0.5 of Malvern (Malvern Panalytical Ltd., Worcester, UK). The employed scan was a Gonio type, using a step of 0.0130° 2Theta and 29.07 s step−1. The Rietveld refinement with Gsas II software (version #5798) were performed for crystal structure parameter calculations of VO2 (M) phase in the samples. Calculations by Williamson Method with software Highscore Plus 3.0.5 of Malvern (Malvern Panalytical Ltd., Worcester, UK).

3. Results and Discussion

Conventional hydrothermal routes for the one-step preparation of VO2(M) typically involve long reaction times, commonly ranging from 20 to 48 h [24,27]. In this work, the synthesis parameters were systematically evaluated to identify the minimum conditions required for stabilizing the monoclinic VO2(M) phase. Based on the analysis of the reversible enthalpy associated with the semiconductor–metal phase transition, a reaction time of 6 h at 270 °C was identified as sufficient to obtain VO2(M), enabling a substantial reduction in synthesis time compared to conventional approaches.
The experimental results further show that strict control of both the solution pH and the reaction atmosphere is essential for the successful synthesis of W-doped VO2(M). Acidic conditions, as well as the presence of oxygen, were found to promote the formation of non-thermochromic vanadium oxide phases. Previous studies have indicated that maintaining the pH within a neutral to slightly basic range favors the controlled nucleation and growth of nanoscale VO2 particles [20,26,34,35]. In line with these observations, a gradual increase in pH was implemented in the present synthesis by the controlled addition of NH3, until a final pH value of 8.5 was reached, enabling the formation of particles.
The elemental composition of the samples was evaluated by energy-dispersive X-ray spectroscopy (EDS) and mapping the vanadium, tungsten, and oxygen emission lines (see Figure 2). The tungsten emission lines (Lα = 8.398 keV and Mα = 1.775 keV) were observed in the W-doped samples and its effect in the thermal behavior was confirmed using differential scanning calorimetry.
Figure 2. Elemental mapping of undoped and W-doped VO2 obtained by energy dispersive spectroscopy on the scanning electron microscope (EDS-SEM). EDS map shows detection of vanadium (cyan), oxygen (green), and tungsten (purple).
Differential Scanning Calorimetry (DSC) showed the reversible phase transition by measuring the heat capacity and the differences in the enthalpy of the two phases under specific conditions. DSC analyses are shown in Figure 3A–C. These results confirmed the reversible phase transition of the obtained hydrothermal VO2 powders, with a first order thermal transition at 59 °C with 18 °C of hysteresis for the undoped sample whereas the thermal hysteresis varied from 19 to 16 °C for 0.5 and 1.0 wt.%, respectively. The phase transition enthalpy of the undoped VO2 sample was found close to 16.0 J g−1 for heating as well as for the cooling process. This value is lower compared to those found for hydrothermal VO2 [24,36], and as expected, decreases for the doped samples [37]. These enthalpy differences may be attributed to variations on the crystallinity degree of the powdered sample (confirmed by XRD), as well as particle sizes. Transition temperature of doped-VO2 with 0.5 as well as 1 wt.% tungsten decreased nearly to 17 °C per tungsten wt.%, this result is similar to those found in the literature for hydrothermally obtained doped-VO2 [26,38], thus confirming the presence of tungsten in the VO2 matrix and its role on tuning the transition temperatures for hydrothermal VO2 [4,39].
Figure 3. Differential scanning calorimetry of (A) Undoped VO2, (B) Doped with 0.5 wt.% W, (C) Doped with 1 wt.% W, using a scan rate of 10 °C min−1 in inert atmosphere. X-Ray Diffraction analysis of hydrothermal-produced VO2 samples of (D) Undoped, (E) Doped with 0.5 wt.% W, (F) Doped with 1 wt.% W. The asterisks (*) indicate weak diffraction peaks that cannot be assigned to VO2(M) reflections and may originate from minor secondary phases.
The crystalline structure of the synthesized VO2 samples was studied by X-ray powder diffraction (XRD) analysis. In the synthesis of hydrothermal VO2, several metastable phases may be formed [40]. Results shown in Figure 3D–F confirmed that most signals can be indexed as the monoclinic VO2(M) phase according to ICCD 04-003-2035 and references found in the literature [35,36,41,42]. Phase confirmation of the oxides in the samples via XRD is complex to define because of the similarities between VO2(M) (P21/c), VO2(R) (P42/mnm) phases [43], the subtle difference between these phases at (−111) and (−102) diffraction planes could be masked because of the amorphous contribution. However, three diffraction peaks in the 2theta range of 47–52° were not assigned to monoclinic VO2. By comparing these peaks with analyses found in the literature, they are most likely to be part of a fraction of metastable VO2(B), formed as part of the hydrothermal synthesis [40]. The low signal-baseline ratio suggests the presence of amorphous material in the sample, supporting the calorimetric results. However, the matching of the diffraction peaks with card ICCD 04-003-2035 VO2 (M) confirmed a rapid hydrothermal synthesis within 6 h. The Rietveld refinement for crystal structure parameter calculations of VO2(M) phase [44] were performed in the samples, this information is shown in Table A1.
The presence of tungsten as a dopant in the samples is difficult to verify by direct assignment of XRD peaks, as observed when comparing E and F with Figure 3D. This behavior can be attributed to the low tungsten content relative to VO2, which likely masks any distinct diffraction signal associated with tungsten, as previously reported in similar studies [26,35].
Nevertheless, the influence of W-doping on the VO2 microstructure is evident in Figure 4, where the main (011) reflection exhibits a gradual shift toward lower diffraction angles as the W content increases, approximately 0.4° in 2Theta per wt.% of W. Williamson–Hall analysis suggests crystallite sizes of 24.2, 24.8, and 34.8 nm for undoped VO2(M), VO2 doped with 0.5 wt.% W, and VO2 doped with 1 wt.% W, respectively. In addition to changes in crystallite size, the observed peak shift may also be influenced by lattice strain induced by tungsten incorporation, as local structural distortions can alter diffraction conditions beyond a simple increase in interplanar spacing [45].
Figure 4. Tungsten doped samples showed a shift in the main diffraction peak towards smaller angles.
This behavior has been previously reported [46,47] and is commonly attributed to the substitution of larger W6+ ions for V4+ ions within the VO2 lattice, leading to an expansion of the interplanar distance [26]. The effect of tungsten doping is further evidenced by an approximate 0.05° broadening of the (011) peak (Figure 4), which is associated with non-uniform crystallite strain [48]. Additionally, differences in ionic radius have been reported to influence the V–O bonding environment, resulting in higher binding energies between vanadium and oxygen [35].
To understand the stability of the W-doped and undoped VO2, the thermogravimetric analysis was conducted in a synthetic air atmosphere, as shown in Appendix A Figure A1. The powder samples were heated in the oxidant atmosphere showing a mass gain due to oxidation, beginning near 350 °C and finishing at 550 °C with a weight gain of ca. 3.0%. The weight gain values of VO2 (M) correspond well to the oxidation of the bulk VO2 to V2O5 [49].
Finally, for dynamic light scattering (DLS) measurements the bulk VO2 was dispersed in xylene using mechanical exfoliation. The powders were dispersed in xylene at a concentration of 1% (m/v). Prior to measurement, the dispersions were sonicated for 1 min at 30% of the maximum amplitude to ensure adequate deagglomeration. The analysis shows agglomerates with particle sizes close to 200 nm in diameter, as shown in Figure 5A.
Figure 5. (A) Dynamic light scattering on the VO2(M) sample in xylene, (B) Transmission electron microscopy images of the obtained VO2(M) particles.
Then, the particles were evaluated by transmission electron microscopy (TEM) analyses (Figure 5B) confirming the formation of microcrystals. The bulk material exfoliation into nanocrystals (larger than 35 nm) using mechanical techniques must be further studied, in order to tailor these thermochromic materials inside a polymeric matrix. The undoped and W-doped VO2 exfoliation is a promising way to tune their properties for the fabrication of low cost thermochromic devices.

4. Conclusions

We demonstrated a fast and low-toxicity hydrothermal-assisted precipitation route for producing thermochromic VO2(M) within only 6 h, without any post-annealing.
A slightly basic precipitation environment (pH ≈ 8.5) was identified as a key requirement for stabilizing the monoclinic VO2(M) phase. The method also enabled effective W incorporation into the VO2 lattice, resulting in a systematic decrease in the phase-transition temperature by approximately 17 °C per wt.% W and crystallite sizes below 35 nm. These outcomes highlight that the proposed route not only simplifies VO2 synthesis but also provides intrinsic control over its thermochromic properties.
The undoped and W-doped powders obtained here represent promising starting materials for smart-window coatings, pending further optimization of particle-size distribution and dispersion in polymeric matrices. Overall, this work provides a practical and scalable synthesis route that supports the development of cost-effective thermochromic VO2-based materials, which may be of interest for energy-efficient building applications in tropical climates.

Author Contributions

Conceptualization, N.M.-Q., R.S.-P. and E.A.S.; Methodology, R.S.-P., E.C. and N.H.-M.; Formal Analysis, F.A.D.-M.; Investigation, N.M.-Q., F.A.-H., R.S.-P., E.C., H.B.R., G.S.-A. and F.A.D.-M.; Writing—Original Draft, N.M.-Q., F.A.-H. and R.S.-P., Writing—Review and Editing, N.M.-Q., E.C. and E.A.S.; Visualization, F.A.-H., Supervision, E.A.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Vicerrectoria de Investigación del Instituto Tecnológico de Costa Rica (Project ID 1450028).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Acknowledgments

During the preparation of this manuscript, the authors used ChatGPT and DALL·E (GPT-5.1, OpenAI) to assist in the conceptual design and initial draft of the graphical abstract. This AI-generated component was reviewed, edited, and finalized by the authors, who take full responsibility for the final content. The authors also acknowledge the Programa de Doctorado Académico en Ingeniería jointly offered by the Universidad de Costa Rica (UCR) and the Instituto Tecnológico de Costa Rica (ITCR) for academic support.

Conflicts of Interest

The authors declare no conflicts of interest.

Appendix A

Appendix A.1. Rietveld Refinement Structure Analysis

Table A1. Rietveld refinement structure parameters for VO2(M) in the samples.

Appendix A.2. TGA Analyses

Figure A1. TGA analyses of synthesized of undoped and W-doped VO2 and in the air atmosphere.

References

  1. Lee, E.; Selkowitz, S.; Bazjanac, V.; Inkarojrit, V.; Kohler, C. High-Performance Commercial Building Facades; Lawrence Berkeley National Laboratory (LBNL): Berkeley, CA, USA, 2002. [Google Scholar] [CrossRef] [Scilit]
  2. Chang, T.; Cao, X. Review on thermochromic vanadium dioxide based smart coatings: From lab to commercial application. Adv. Manuf. 2018, 6, 1–19. [Google Scholar] [CrossRef] [Scilit]
  3. Li, M.; Magdassi, S.; Gao, Y.; Long, Y. Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows. Small 2017, 13, 1701147. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  4. Kamalisarvestani, M.; Saidur, R.; Mekhilef, S.; Javadi, F.S. Performance, materials and coating technologies of thermochromic thin films on smart windows. Renew. Sustain. Energy Rev. 2013, 26, 353–364. [Google Scholar] [CrossRef] [Scilit]
  5. Carmody, J.; Lee, E.S.; Clear, R. Window Systems for High-Performance Buildings; Norton: San Francisco, CA, USA, 2004. [Google Scholar]
  6. Granqvist, C.G.; Lansåker, P.C.; Mlyuka, N.R.; Niklasson, G.A.; Avendaño, E. Progress in chromogenics: New results for electrochromic and thermochromic materials and devices. Sol. Energy Mater. Sol. Cells 2009, 93, 2032–2039. [Google Scholar] [CrossRef] [Scilit]
  7. Yoon, J.; Kim, K.S.; Hong, W.K. Thermochromic Vanadium Dioxide Nanostructures for Smart Windows and Radiative Cooling. Chem.–A Eur. J. 2024, 30, e202400826. [Google Scholar] [CrossRef] [Scilit]
  8. Granqvist, C.G.; Niklasson, G.A. Thermochromic oxide-based thin films and nanoparticle composites for energy-efficient glazings. Buildings 2017, 7, 3. [Google Scholar] [CrossRef] [Scilit]
  9. Gagaoudakis, E.; Aperathitis, E.; Michail, G.; Panagopoulou, M.; Katerinopoulou, D. Low-temperature rf sputtered VO2 thin fi lms as thermochromic coatings for smart glazing systems. Sol. Energy 2018, 165, 115–121. [Google Scholar] [CrossRef] [Scilit]
  10. Cui, Y.; Ke, Y.; Liu, C.; Chen, Z.; Wang, N.; Zhang, L.; Zhou, Y.; Wang, S.; Gao, Y.; Long, Y. Thermochromic VO2 for Energy-Efficient Smart Windows. Joule 2018, 2, 1707–1746. [Google Scholar] [CrossRef] [Scilit]
  11. Madida, I.G.; Simo, A.; Sone, B.; Maity, A.; Kana, J.K.; Gibaud, A.; Merad, G.; Thema, F.; Maaza, M. Submicronic VO2-PVP composites coatings for smart windows applications and solar heat management. Sol. Energy 2014, 107, 758–769. [Google Scholar] [CrossRef] [Scilit]
  12. Zhou, J.; Gao, Y.; Zhang, Z.; Luo, H.; Cao, C.; Chen, Z.; Dai, L.; Liu, X. VO2 thermochromic smart window for energy savings and generation. Sci. Rep. 2013, 3, 3029. [Google Scholar] [CrossRef] [Scilit]
  13. Shi, J.; Zhou, S.; You, B.; Wu, L. Preparation and thermochromic property of tungsten-doped vanadium dioxide particles. Sol. Energy Mater. Sol. Cells 2007, 91, 1856–1862. [Google Scholar] [CrossRef] [Scilit]
  14. Warwick, M.E.A.; Binions, R. Advances in thermochromic vanadium dioxide films. J. Mater. Chem. A 2014, 2, 3275–3292. [Google Scholar] [CrossRef] [Scilit]
  15. Leroux, C.; Nihoul, G.; Van Tendeloo, G. From to Theoretical structures of polymorphs and in situ electron microscopy. Phys. Rev. B Condens. Matter Mater. Phys. 1998, 57, 5111–5121. [Google Scholar] [CrossRef] [Scilit]
  16. Wang, N.; Goh, Q.S.; Lee, P.L.; Magdassi, S.; Long, Y. One-step hydrothermal synthesis of rare earth/W-codoped VO2 nanoparticles: Reduced phase transition temperature and improved thermochromic properties. J. Alloy Compd. 2017, 711, 222–228. [Google Scholar] [CrossRef] [Scilit]
  17. Zhu, J.; Zhou, Y.; Wang, B.; Zheng, J.; Ji, S.; Yao, H.; Luo, H.; Jin, P. Vanadium Dioxide Nanoparticle-based Thermochromic Smart Coating: High Luminous Transmittance, Excellent Solar Regulation Efficiency, and Near Room Temperature Phase Transition. ACS Appl. Mater. Interfaces 2015, 7, 27796–27803. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  18. Jiang, C.; He, L.; Xuan, Q.; Liao, Y.; Dai, J.-G.; Lei, D. Phase-change VO2-based thermochromic smart windows. Light Sci. Appl. 2024, 13, 255. [Google Scholar] [CrossRef] [Scilit]
  19. Li, W.; Ji, S.; Li, Y.; Huang, A.; Luo, H.; Jin, P. Synthesis of VO2 nanoparticles by a hydrothermal-assisted homogeneous precipitation approach for thermochromic applications. RSC Adv. 2014, 4, 13026–13033. [Google Scholar] [CrossRef] [Scilit]
  20. Song, X.; Xu, Z.; Wei, D.; Yue, X.; Zhang, T.; Zhang, H.; Zhang, J.; Dai, Z.; Yao, J. Application of W-Doped VO2 Phase Transition Mechanism and Improvement of Hydrophobic Self-Cleaning Properties to Smart Windows. Photonics 2023, 10, 1198. [Google Scholar] [CrossRef] [Scilit]
  21. Thangappan, R.; Kumar, R.D.; Jayavel, R. Facile hydrothermal synthesis of monoclinic VO2/graphene nanowhisker composite for enhanced performance electrode material for energy storage applications. Diam. Relat. Mater. 2023, 137, 110102. [Google Scholar] [CrossRef] [Scilit]
  22. Piccirillo, C.; Binions, R.; Parkin, I.P. Synthesis and functional properties of vanadium oxides: V2O3, VO2 and V2O5 deposited on glass by aerosol-assisted CVD. Chem. Vap. Depos. 2007, 13, 145–151. [Google Scholar] [CrossRef] [Scilit]
  23. Popuri, S.R.; Miclau, M.; Artemenko, A.; Labrugere, C.; Villesuzanne, A.; Pollet, M. Rapid hydrothermal synthesis of VO2 (B) and its conversion to thermochromic VO2 (M1). Inorg. Chem. 2013, 52, 4780–4785. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  24. Qi, J.; Niu, C. Characterization and Thermodynamic Analysis of VO2 Synthesized by NH4VO3. Energy Procedia 2012, 17, 1953–1959. [Google Scholar] [CrossRef] [Scilit]
  25. Habtemariam, A.B.; Maaza, M. One-pot Hydrothermal Synthesis of Vanadium Dioxide Nanoparticles. Biointerface Res. Appl. Chem. 2023, 13, 361. [Google Scholar]
  26. Dong, B.; Shen, N.; Cao, C.; Chen, Z.; Luo, H.; Gao, Y. Phase and morphology evolution of VO2 nanoparticles using a novel hydrothermal system for thermochromic applications: The growth mechanism and effect of ammonium (NH4+). RSC Adv. 2016, 6, 81559–81568. [Google Scholar] [CrossRef] [Scilit]
  27. Guo, D.; Ling, C.; Wang, C.; Wang, D.; Li, J.; Zhao, Z.; Wang, Z.; Zhao, Y.; Zhang, J.; Jin, H. Hydrothermal One-Step Synthesis of Highly Dispersed M-Phase VO2 Nanocrystals and Application to Flexible Thermochromic Film. ACS Appl. Mater. Interfaces 2018, 10, 28627–28634. [Google Scholar] [CrossRef] [Scilit]
  28. Darmanto, N.S.; Varquez, A.C.G.; Kawano, N.; Kanda, M. Future urban climate projection in a tropical megacity based on global climate change and local urbanization scenarios. Urban Clim. 2019, 29, 100482. [Google Scholar] [CrossRef] [Scilit]
  29. Lyra, A.; Imbach, P.; Rodriguez, D.; Chou, S.C.; Georgiou, S.; Garofolo, L. Projections of climate change impacts on central America tropical rainforest. Clim. Change 2017, 141, 93–105. [Google Scholar] [CrossRef] [Scilit]
  30. Mahdavinejad, M.; Bemanian, M.; Khaksar, N. Choosing Efficient Types of Smart Windows in Tropical Region Regarding to Their Advantages and Productivities 2. Various functions of Smart Windows. Int. Conf. Comput. Commun. Manag. 2011, 5, 335–339. [Google Scholar]
  31. Saeli, M.; Piccirillo, C.; Parkin, I.P.; Binions, R.; Ridley, I. Energy modelling studies of thermochromic glazing. Energy Build. 2010, 42, 1666–1673. [Google Scholar] [CrossRef] [Scilit]
  32. Warwick, M.E.A.; Ridley, I.; Binions, R. Variation of thermochromic glazing systems transition temperature, hysteresis gradient and width effect on energy efficiency. Buildings 2016, 6, 22. [Google Scholar] [CrossRef] [Scilit]
  33. Siddiq, N.A.; Hendinata, L.K. Assessing the Potential of Smart Windows for Energy Efficiency in Tropical Buildings: A Review of Current Research and Future Directions. J. Phys. Conf. Ser. 2024, 2828, 012008. [Google Scholar] [CrossRef] [Scilit]
  34. Okada, M.; Kuno, M.; Yamada, Y. Fast synthesis of monoclinic VO2 nanoparticles by microwave-assisted hydrothermal method and application to high-performance thermochromic film. Sol. Energy Mater. Sol. Cells 2023, 255, 112311. [Google Scholar] [CrossRef] [Scilit]
  35. Li, B.; Tian, S.; Tao, H.; Zhao, X. Tungsten doped M-phase VO2 mesoporous nanocrystals with enhanced comprehensive thermochromic properties for smart windows. Ceram. Int. 2019, 45, 4342–4350. [Google Scholar] [CrossRef] [Scilit]
  36. Mao, Z.; Wang, W.; Liu, Y.; Zhang, L.; Xu, H.; Zhong, Y. Infrared stealth property based on semiconductor (M)-to-metallic (R) phase transition characteristics of W-doped VO2 thin films coated on cotton fabrics. Thin Solid Film. 2014, 558, 208–214. [Google Scholar] [CrossRef] [Scilit]
  37. Li, W.; Ji, S.; Qian, K.; Jin, P. Preparation and characterization of VO2–BaSO4 composite films with enhanced optical properties in thermochromic field. Ceram. Int. 2015, 41, 5049–5056. [Google Scholar] [CrossRef] [Scilit]
  38. Zhang, L.; Xia, F.; Yao, J.; Zhu, T.; Xia, H.; Yang, G.; Liu, B.; Gao, Y. Facile synthesis, formation mechanism and thermochromic properties of W-doped VO2 (M) nanoparticles for smart window applications. J. Mater. Chem. C 2020, 8, 13396–13404. [Google Scholar] [CrossRef] [Scilit]
  39. Chen, S.E.; Lu, H.H.; Brahma, S.; Huang, J.L. Effects of annealing on thermochromic properties of W-doped vanadium dioxide thin films deposited by electron beam evaporation. Thin Solid Film. 2017, 644, 52–56. [Google Scholar] [CrossRef] [Scilit]
  40. Zhang, Y.; Tan, X.; Huang, C.; Meng, C. Hydrothermal treatment with VO2(B) nanobelts for synthesis of VO2(A) and W doped VO2(M) nanobelts. Mater. Res. Innov. 2015, 19, 295–302. [Google Scholar] [CrossRef] [Scilit]
  41. Saini, M.; Dehiya, B.S.; Umar, A.; Goyat, M.S. Phase modulation in nanocrystalline vanadium di-oxide (VO2) nanostructures using citric acid via one pot hydrothermal method. Ceram. Int. 2019, 45, 18452–18461. [Google Scholar] [CrossRef] [Scilit]
  42. Gagaoudakis, E.; Mantsiou, E.; Zouridi, L.; Aperathitis, E.; Binas, V. Lab- and Large-Scale Hydrothermal Synthesis of Vanadium Dioxide Thermochromic Powder. Crystals 2025, 15, 668. [Google Scholar] [CrossRef] [Scilit]
  43. Edalati, K.; Fujita, I.; Sauvage, X.; Arita, M.; Horita, Z. Microstructure and phase transformations of silica glass and vanadium oxide by severe plastic deformation via high-pressure torsion straining. J. Alloy Compd. 2019, 779, 394–398. [Google Scholar] [CrossRef] [Scilit]
  44. Toby, B.H.; Von Dreele, R.B. GSAS-II: The genesis of a modern open-source all purpose crystallography software package. J. Appl. Crystallogr. 2013, 46, 544–549. [Google Scholar] [CrossRef] [Scilit]
  45. Guan, D.; Shi, C.; Xu, H.; Gu, Y.; Zhong, J.; Sha, Y.; Hu, Z.; Ni, M.; Shao, Z. Simultaneously mastering operando strain and reconstruction effects via phase-segregation strategy for enhanced oxygen-evolving electrocatalysis. J. Energy Chem. 2023, 82, 572–580. [Google Scholar] [CrossRef] [Scilit]
  46. Chen, R.; Miao, L.; Liu, C.; Zhou, J.; Cheng, H.; Asaka, T.; Iwamoto, Y.; Tanemura, S. Shape-controlled synthesis and influence of W doping and oxygen nonstoichiometry on the phase transition of VO2. Sci. Rep. 2015, 5, srep14087. [Google Scholar] [CrossRef] [Scilit]
  47. Singh, D.U.; Narayanan, R. Temperature tunable flexible photo absorbers based on near-infrared 1D photonic crystal hybridized W-doped VO2 nanostructures. Nanotechnology 2021, 33, 065204. [Google Scholar] [CrossRef] [Scilit]
  48. Waseda, Y.; Matsubara, E.; Shinoda, K. Diffraction from Polycrystalline Samples and Determination of Crystal Structure. In X-Ray Diffraction Crystallography; Springer: Berlin/Heidelberg, Germany, 2011; pp. 107–168. [Google Scholar] [CrossRef] [Scilit]
  49. Ji, H.; Liu, D.; Cheng, H.; Zhang, C.; Yang, L.; Ren, D. Infrared thermochromic properties of monoclinic VO2 nanopowders using a malic acid-assisted hydrothermal method for adaptive camouflage. RSC Adv. 2017, 7, 5189–5194. [Google Scholar] [CrossRef] [Scilit]
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