Search Results (1,437)

Commercial lead zirconate titanate (PZT) ceramics are widely employed in electromechanical devices due to their excellent piezoelectric response and operational stability. This study investigates the influence of polarization temperature and time on the electromechanical performance of commercial Sparkler PZT-4 (Navy Type I) ceramics. Samples were compacted, sintered at 1230 °C, and polarized under temperatures ranging from 80 to 110 °C for 2, 8, and 15 min using a constant electric field of 3.0 kV/mm. Microstructural, physical, and crystallographic analyses confirmed the successful processing of the ceramics, yielding an apparent density of 7.68 g/cm³, relative density of 96.02%, and the predominance of the tetragonal Pb(Zr,Ti)O₃ perovskite phase. Electromechanical characterization revealed a strong dependence of the piezoelectric coefficient (d₃₃) and electromechanical coupling factor (K_p) on the polarization conditions. Maximum values of d₃₃ = 325.8 pC/N and K_p = 0.509 were obtained under elevated temperatures and longer polarization times. A phenomenological Avrami approach indicated faster apparent domain alignment at higher temperatures, while ANOVA and Tukey tests confirmed the significant influence of polarization parameters on the electromechanical response. The results identify favorable polarization conditions for commercial PZT-4 ceramics used in sensors, actuators, and ultrasonic transducers. Full article

Numerous space missions are advancing our understanding of the origin and evolution of planetary bodies and the potential for the emergence of life throughout the Solar System and beyond. Investigations across the inner Solar System have revealed contrasting planetary environments: Venus offers insights into runaway greenhouse processes, while Mars remains a primary target for studying climate evolution, atmospheric loss, past water activity, and extinct life, with sample return missions planned in the next decade. Beyond the traditional habitable zone, attention has shifted to the icy moons of Jupiter and Saturn. Data from space missions have identified subsurface oceans and possibly active geology on moons such as Europa, Ganymede, Titan, and Enceladus, highlighting their astrobiological potential. Among others, Europa’s ocean, possibly interacting with a silicate mantle and sustained by tidal heating, Enceladus plumes and Titan’s complex organic chemistry make these worlds compelling targets. Current and upcoming missions will further explore these environments and refine our understanding of habitability. This work also emphasizes the importance of planetary protection to prevent biological contamination, particularly for sample return missions. Continued exploration, supported by international collaboration and technological innovation, will be essential to address engineering challenges and to expand our knowledge of potentially habitable environments across the Solar System. Full article

As multilayer ceramic capacitors continue to evolve toward thinner dielectric layers and lower cost, the development of barium titanate powders combining nano-scale particle size with reduction resistance has become a critical industry demand. In this paper, BT-xOH nano-powders with different hydroxyl defect contents were prepared by the sol–gel–hydrothermal method through adjusting the concentration of the mineralizer KOH, and the regulation mechanism of hydroxyl defects on the reduction resistance of barium titanate ceramics was systematically investigated. The research shows that for BT-xOH ceramics sintered under a reducing atmosphere, hydroxyl defects are converted into oxygen vacancies, disrupting the long-range order of ferroelectric domains and associating with barium vacancies to form [${\mathrm{V}}_{\mathrm{Ba}}^{‘’}\text{-}{\mathrm{V}}_{\mathrm{O}}^{..}$] defect dipoles. These dipoles, in coordination with the increase in grain boundary density, enhance the charge carrier migration barrier and the suppression of oxygen vacancies and electronic conductivity by the grain boundary space charge layer, resulting in a resistivity on the order of 10¹¹ Ω·cm under a reducing atmosphere. Meanwhile, oxygen vacancies generate a pinning effect at grain boundaries, achieving the effect of inhibiting grain growth. This study reveals the microscopic mechanism by which the reduction resistance is enhanced through the regulation of intrinsic hydroxyl defects in the powder, providing a new technical pathway for dielectric materials used in high-performance base metal electrode MLCCs. Full article

Ba₂Li_2/3Ti_16/3O₁₃ (BLTO) tunnel structure titanate was successfully synthesized using a solvothermal methodology evaluating the effect of different solvents (isopropanol, ethylene glycol, and propylene glycol) on structural, optical, and electronic properties, as well as on photocatalytic hydrogen production using methanol as a sacrificial agent. The structural characterization revealed that the synthesis solvent greatly influences the phase purity, with ethylene glycol being the one that promoted the formation of a purer BLTO phase (96.1%), while the samples prepared with other solvents exhibited slightly higher amounts of BaTiO₃, and BaTi₅O₁₁ impurities. All samples showed similar morphology and bandgap; however, differences in surface-defect chemistry were observed. In particular, the sample prepared using ethylene glycol exhibited a higher concentration of oxygen vacancies, which contributed to a more efficient separation of the photogenerated charges, as evidenced by the photoluminescence measurements. As a result, this sample showed enhanced photoactivity for hydrogen production. Additionally, it was observed that the BLTO material exhibited good stability over repeated irradiation cycles, highlighting its potential as a photocatalyst for hydrogen generation. Full article

Integration of lead zirconate titanate (PZT) films on metallic substrates is important for flexible piezoelectric devices, but achieving highly textured crystallinity without detrimental interfacial diffusion or oxidation remains challenging. In this work, PZT thick films (~1.3 μm) were deposited on titanium substrates using radio-frequency magnetron sputtering at 400 °C followed by rapid thermal processing at 640 °C for 2.5 min. A conductive LaNiO₃ buffer layer was introduced to promote the nucleation of the perovskite phase and suppress interfacial degradation. The resulting PZT films on the LNO/Pt/Ti substrates exhibit a strong (001) preferred orientation and a dense microstructure. The films show a large remnant polarization P_r of ~61 μC cm⁻² and a low coercive field E_c of ~56 kV cm⁻¹ at 60 V, together with a dielectric constant ε_r of ~1350–1612 and a dielectric loss tanδ ≤ 0.06 in the frequency range of 1 kHz to 1 MHz. Patterned Pt/PZT/LNO/Pt/Ti cantilevers yield a transverse piezoelectric coefficient e_31,f of ~−6.7 C/m², significantly outperforming reported piezoelectric films deposited on Ti. These results demonstrate that controlled nucleation and rapid thermal crystallization enable highly textured PZT films on reactive metallic substrates, providing a viable route for flexible piezoelectric MEMS devices. Full article

Nitrogen-containing molecules are fundamental components of astrobiology and play a key role in planetary environments. These species are particularly important because they may serve as key precursors to prebiotic molecules and contribute to chemical complexity. Reactions involving the highly reactive species methylidyne (CH) play a key role in complex organic formation in astrochemical environments, yet their interactions with nitriles such as acetonitrile (CH₃CN) remain relatively unexplored. In this work, we investigate the reaction network of CH + CH₃CN using high-level quantum-chemical calculations with RRKM and microcanonical transition-state theories to characterize the relative energies of reactants, intermediates, transition states, and products to identify the most favorable reaction pathways. Our results reveal that the most energetically favorable reaction channels proceed via barrierless CH addition to the triple CN bond and three-membered ring opening or CH insertion into a C-H bond, followed by a hydrogen elimination to form acrylonitrile (C₂H₃CN). This route highlights an efficient pathway toward a molecule of astrobiological interest. Acrylonitrile is particularly significant due to its stability and dual functional groups, which enable molecular growth complexity, both in planetary atmospheres and on surfaces, under astrochemical conditions. In addition to acrylonitrile, we identified a few other competing channels leading to an isonitrile species, which emphasizes a previously unexplored aspect of isomerization chemistry in the atmospheric planetary science. These isonitrile products, while less abundant, provide insight to the diversity of nitrogen-containing molecules that may form in environments such as Titan’s atmosphere or the interstellar medium. In these environments, acrylonitrile may serve as a reactive precursor that facilitates cyclization and molecular growth, which enables the formation of nitrogen-containing polycyclic aromatic molecules and N-heterocycles. This, in turn, contributes to the emergence of larger, more complex organic species relevant to prebiotic chemistry and potential origin of life in our solar system. Full article

Lignin is one of the most abundant biopolymers in nature. The major challenge in lignin depolymerization lies in the formation of complex mixtures that require extensive downstream separation. Selective depolymerization strategies aim to overcome this limitation by promoting controlled bond cleavage while suppressing undesired secondary reactions. In this work, a series of rare-earth-free, perovskite-type mixed metal oxides with general compositions Zn_xNi_1–xTiO₃ and Cu_yNi_1–yTiO₃ were synthesized and evaluated as heterogeneous catalysts for the base-catalyzed depolymerization of lignin. Among the investigated materials, CuTiO₃ exhibited superior catalytic performance, enabling the formation of vanillin as the dominant monomer with high selectivity. The selected catalyst was further characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The combined effects of key reaction parameters, including temperature, pressure, lignin-to-catalyst ratio, NaOH concentration, and reaction time, were systematically investigated using response surface methodology (RSM). Under the optimized conditions (154 °C, 0.3 MPa, lignin-to-catalyst ratio of 24.5:1, 10 mL of 0.5 M NaOH, and 12 h reaction time), a monomer yield of 11.5 ± 0.46% with ~81% GC-selectivity toward vanillin was achieved. These findings demonstrate that perovskite-type titanates can serve as robust and reusable catalysts. Full article

The search for efficient photocatalysts for sustainable hydrogen production has driven growing interest in barium titanate (BaTiO₃)-based materials, particularly through polymorph control, surface engineering, and nonmetal and transition-metal doping. In this work, we provide an atomic-scale understanding of structural modifications in nitrogen-, fluorine-, and rhodium-doped BaTiO₃ using Density Functional Theory (DFT), as well as pristine and fluorine-substituted BaTiO₃ using reactive force-field molecular dynamics (ReaxFF-MD) simulations. DFT results for pristine and doped tetragonal BaTiO₃, as well as pristine hexagonal BaTiO₃, reveal that nitrogen and rhodium substitutions enhance the covalent character of Ti-N and Rh-O bonds and promote the redistribution of electron density, as evidenced by noncovalent interaction (NCI) and critical point (QTAIM) analyses, whereas fluorine substitution leads to more ionic Ti-F bonding. ReaxFF-MD simulations of pristine and fluorine-substituted BaTiO₃ in contact with water molecules demonstrate that fluorine substitution suppresses interfacial O-H bond formation and promotes ordered molecular hydration layers near titanium sites, as reflected in bond statistics and radial distribution functions. This study provides molecular insights into the role of N, F, and Rh doping in BaTiO₃ using DFT, and the role of fluorine doping in BaTiO₃ at the water–solid interface using ReaxFF-MD simulations, demonstrating that this integrated computational approach provides a solid basis for the rational design of next-generation materials for energy-related applications. Direct calculations of photocatalytic activity, charge transfer rates, and ferroelectric polarization effects were not performed in this work and remain important directions for future study. Full article

High-emissivity coatings on flexible fibrous fabrics are promising thermal-insulation materials for thermal protection systems in hypersonic vehicles. However, the interfacial bonding strength between the high-emissivity coating and the flexible fibrous substrate remains a critical challenge. A high-emissivity double-layer TiO₂ interlayer modified by metal ions (Mg²⁺, Co²⁺, Ni²⁺, and Zn²⁺) with high-entropy (M²⁺@TiO₂-HE) coating was developed on an aluminosilicate fiber fabric. The interlayer of the M²⁺@TiO₂-HE coating not only enhances bonding strength through mechanical interlocking but also improves thermal insulation performance by acting as an infrared reflective layer. The bonding strength between the M²⁺@TiO₂-HE coating and the ASFF substrate showed an 183% enhancement compared to that of the single-layer high-emissivity high-entropy coating. Under one-sided heating at 1400 °C, the backside temperature of the coated ASFF stabilizes at 330 °C, which is approximately 50 °C lower than that of the sample with the single-layer high-emissivity high-entropy coating. In the wavelength range of 0.3–2.0 μm, the average reflectivity of the M²⁺@TiO₂ coating was 0.70, and in the wavelength range of 1–14 μm, the average emissivity of the M²⁺@TiO₂-HE coating was 0.89. The M²⁺@TiO₂-HE coating with high emissivity and reflectivity enhances both the bonding strength and thermal insulation performance of ASFF, showing its potential for applications in aerospace thermal protection systems. Full article

The search for extraterrestrial life has traditionally focused on environments where liquid H₂O is stable over long timescales, such as subsurface aquifers, hydrothermal systems, or ice-rich deposits. However, many planetary bodies are characterized by active cycles of particulate transport involving either mineral dust or atmospheric aerosols. In planetary science, these are commonly distinguished as refractory particles (non-volatile mineral dust) and volatile or mixed aerosol particles, including condensates such as ices, organics, or acidic droplets. Here, we propose the concept of planetary aerobiomes, defined as distributed particle-associated microbial persistence and dispersal systems in extraterrestrial environments. In this framework, refractory mineral particles may act as mobile particle-associated microenvironments that could support microbial survival and dispersal, while in some cases also providing partial physical shielding from environmental stressors. Drawing on observations from terrestrial dust-associated microbiomes and mineral–microbe interactions, particle-associated systems may represent previously overlooked ecological substrates in planetary environments. Rather than replacing models centred on environments with persistent liquid H₂O, this perspective expands them by considering particle-associated microenvironments as transient but potentially relevant biosignature-preservation niches in arid, dust-dominated worlds such as Mars, as well as in aerosol-rich environments including Titan, Venus, and icy moons. We further discuss the implications for life-detection strategies, highlighting atmospheric particles as potential reservoirs of biosignatures, and consider their relevance for applied microbiology, including in situ resource utilization (ISRU) and bioregenerative life-support systems (BLSS). Beyond astrobiological implications, understanding microbial persistence within particle-associated extreme environments may provide useful models for applied microbiology, including stress-resilient microbial engineering, biomining, contamination control, and bioregenerative technologies for space exploration. Full article

The photocatalytic activity of semiconductors can be tuned by changing their morphological or structural properties. However, a simpler and direct method is the introduction of a cocatalyst, for example V₂O₅ or V₂O₅/V₄O₉. In the present work, this was the cocatalyst added to SrTiO₃. The deposition method was directed in such a way that the cocatalyst did not cover the surface of the SrTiO₃ completely. This way, the photocatalytic process (phenol conversion) takes place at the surface of the main catalyst, while the lifetime of the generated charge carriers is increased through electron trapping via the presence of vanadium oxides. The V₂O₅/V₄O₉ cocatalyst influences the recombination processes of excited electrons in SrTiO₃ by modifying the near-surface defects of SrTiO₃, and it can efficiently capture electrons due to the formed heterojunction. The V₄O₉ content enables efficient electron transfer, as its structure can accommodate V⁴⁺ in addition to V⁵⁺. Therefore, a mixed-phase semiconductor is more suitable as a cocatalyst than a single-phase semiconductor. In this work, the photocatalytic activity of SrTiO₃ was investigated in the presence of V₂O₅ (0–20 wt.%). It was found that all the samples that contained the cocatalyst showed higher photocatalytic activity than the unmodified SrTiO₃. The sample containing 10 wt.% of cocatalyst performed ~5.4 times better than pristine SrTiO₃ (35.87 µmol_phenol/g_catalyst, vs. 7.74 µmol_phenol/g_catalyst). This sample also contains a relatively high amount of V₄O₉ compared to the other samples, in addition to V₂O₅, which may be the main reason for the enhanced photocatalytic performance. Full article

Calcium copper titanate (CaCu₃Ti₄O₁₂, abbreviated as CCTO) has emerged as a versatile, high-performance material distinguished by its remarkable dielectric, photocatalytic, and environmental properties, positioning it at the forefront of ongoing research and technological innovation. This review provides a comprehensive analysis of CCTO, emphasizing its growing relevance in catalytic and environmental applications. Beginning with an overview of its unique structural and dielectric properties, we discuss how these attributes underpin CCTO’s multifunctionality. Various synthesis methods are examined for their effects on CCTO’s microstructure and performance. Furthermore, we investigate the photocatalytic potential of CCTO under visible light, particularly for applications such as water splitting, CO₂ reduction, and degradation of organic pollutants. Environmental applications, including gas sensing and wastewater treatment, are also evaluated, highlighting CCTO’s chemical robustness and suitability under diverse operating conditions. Lastly, key challenges in scalability, cost, and environmental adaptability are discussed, along with future directions, including hybrid composite development and machine-learning-assisted material design. Together, these insights position CCTO as a promising material for advancing sustainable technologies in energy and the environment. Full article

Flexible piezoelectric fibers are promising materials for next-generation wearable and flexible electronic devices due to their lightweight structure, mechanical flexibility, and electromechanical response. In this study, BaTiO₃/PVDF composite fibers were prepared by melt spinning under an electrostatic field, followed by thermal drawing to enhance the electroactive phase content. The effects of BaTiO₃ loading, draw ratio, thermal stretching ratio, stretching rate, and electric field strength on the crystalline structure of the fibers were systematically investigated. Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and electron microscopy were used to evaluate phase evolution, crystallinity, and filler distribution. The results showed that the processing conditions significantly influenced the transformation of PVDF from the α-phase to the electroactive β-phase. The optimized fibers were obtained at 1 wt.% BaTiO₃, a thermal stretching ratio of 5, a stretching rate of 40 mm/min, and an electric field strength of 18 kV, resulting in a crystallinity of 61.3% and a β-phase content of 95.5%. The enhanced structural characteristics indicate the strong potential of the developed composite fibers for flexible electroactive applications, though direct electromechanical characterization is required for device integration. Full article

Polymer–ceramic piezoelectric composites are widely investigated to combine the high piezoelectric performance of ferroelectric ceramics with the flexibility and processability of electroactive polymers. However, achieving enhanced dielectric properties while preserving the intrinsic piezoelectric response of the polymer matrix remains challenging, particularly due to dielectric mismatch between the constituent phases and interfacial effects. In this work, barium titanate (BaTiO₃) loaded poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) nanocomposites were fabricated by solvent casting using polyvinylpyrrolidone (PVP) and polysorbate 80 (PS80) as dispersing agents, aiming to obtain polarizable materials capable of retaining high piezoelectric strain coefficient (d₃₃) values and potentially exploiting the opposite polarity of matrix and filler through tailored poling strategies. Morphological, crystallographic, structural, thermal, thermomechanical, dielectric, and piezoelectric characterizations were performed by SEM/EDXS, XRD, FTIR, DSC, TGA, DMTA, dielectric spectroscopy, and d₃₃ measurements. Both dispersants improved filler dispersion and film densification, increasing the crystalline fraction of the matrix, without altering the relative fraction of β-phase (up to 93%). PVP enabled moderate and stable permittivity enhancement with weak frequency dependence, whereas PS80 introduced an electrically active interfacial contribution that amplified low-frequency permittivity at high filler loadings but made the permittivity more frequency-dependent. The piezoelectric response (between −20 pC/N and −25 pC/N) remained predominantly governed by the polymer phase, suggesting limited polarization played by BaTiO₃. These results underlined the critical role of interfacial electrical properties in designing stable high-performance flexible PVDF-TrFE/BaTiO₃ composites. Full article

Foundation models are reshaping computational pathology by enabling scalable task-agnostic representations of histopathological whole-slide images (WSIs). Unlike earlier task-specific deep learning systems, pathology foundation models (PFMs) leverage massive whole-slide image repositories and self-supervised Vision Transformer architectures to achieve broad generalization and few-shot adaptability. Their evolution reflects a shift from weakly supervised approaches such as Clustering-Constrained Attention Multiple Instance Learning (CLAM) and hierarchical architectures such as Hierarchical Image Pyramid Transformer (HIPT) to large-scale efforts including foundation models, UNI, Virchow, Phikon, CONtrastive learning from Captions for Histopathology (CONCH), GigaPath, H-Optimus, Transformer-Based Pathology Image and Text Alignment Network (TITAN), and the Mayo Clinic Atlas. These models demonstrate impressive performance across diagnostic and prognostic benchmarks while also opening pathways for multimodal integration with genomics and clinical data. Yet significant barriers remain including inconsistent generalization across institutions, interpretability lagging behind clinical needs, and slow integration into routine laboratory workflows. Certain domains of anatomic pathology such as cytopathology, transplant pathology, frozen sections, and rare tumor subtypes remain particularly resistant to current models. Here, we review the development of PFMs, critically evaluate their strengths and limitations, and outline priorities for their safe and effective clinical translation. We argue that the next phase of PFM development will depend on rigorous benchmarking, pathologist-in-the-loop deployment, and multimodal fusion ensuring these models evolve from research tools into clinically robust systems. Full article