Search Results (66)

Electrocaloric materials, which exhibit adiabatic temperature change under an applied electric field, are promising for solid-state cooling technologies. In this study, the electrocaloric response of lead-free Ba_xCa_1−xZr_yTi_1−yO₃ (BCZT) ceramics was modeled to investigate the effects of composition, processing, and measurement conditions on performance. A high-accuracy XGBoost regression model (R² = 0.99, MAE = 0.02 °C) was developed using a dataset of 2188 literature-derived data points to predict and design the electrocaloric response of BCZT ceramics. The feature space incorporated compositional ratios, processing parameters, measurement settings, and atomic-level Magpie descriptors, along with Curie temperature to account for phase-transition behavior. Feature importance analysis revealed that electric field, measurement temperature, and proximity to the Curie point are the most critical factors influencing ΔT_EC. Bayesian optimization was applied to navigate the design space and identify performance maxima under unconstrained and realistic constraints, offering valuable insights into the nonlinear interactions governing electrocaloric performance. Under room temperature and moderate-field conditions (24 °C, 40 kV/cm), the optimized ΔT_EC achieved a value of 1.03 °C for Ba_0.85Ca_0.15Zr_0.40Ti_0.60, to be processed at 1090 °C for 3 h during calcination, 1300 °C for 2 h during sintering. By integrating experimental insight with machine learning and optimization, this study offers a refined, interpretable framework for accelerating the design of high-performance electrocaloric ceramics while reducing the experimental workload. Full article

Polymer-matrix composites with ceramic fillers have various applications, one of which is the modification of the electric field. For this purpose, in this work, high-permittivity silicone composites with different polarization titanates were produced by mechanical mixing. The ceramic fillers chosen were CaCu₃Ti₄O₁₂, K_xFe_yTi_8−yO₁₆, and BaTiO₃ powders with high permittivity values and uniformly distributed in the polymer volume. Ceramic powders were studied by X-ray phase analysis and scanning electron microscopy methods. The proportion of ceramic powder was 25 wt.%. In parallel, composites were prepared with the addition of 25 wt.% glycerin. The functional properties of silicone composites were studied using the following parameters: the electrical strength and permittivity. The addition of all types of ceramic fillers, both together and without glycerin, led to a decrease in electrical strength (below 15 kV·mm⁻¹); the exception is the sample with the CCTO without glycerin (about 28 kV·mm⁻¹). The permittivity and the dielectric loss tangent of the composites increased as a result of the addition of fillers, especially noticeable in combination with glycerol in the low-frequency region. The obtained results are in good agreement with the literature data and can be used in the field of insulation in a high-permittivity layer to equalize equipotential fields. Full article

Solid-state electrolytes for lithium-ion batteries, which enable a significant increase in storage capacity, are at the forefront of alternative energy storage systems due to their attractive properties such as wide electrochemical stability window, relatively superior contact stability against Li metal, inherently dendrite inhibition, and a wide range of temperature functionality. NASICON-type solid electrolytes are an exciting candidate within ceramic electrolytes due to their high ionic conductivity and low moisture sensitivity, making them a prime candidate for pure oxidic and hybrid ceramic-in-polymer composite electrolytes. Here, we report on producing pure and Y-doped Lithium Aluminum Titanium Phosphate (LATP) nanoparticles by spray-flame synthesis. The as-synthesized samples consist of an amorphous component and anatase-TiO₂ crystalline particles. Brief annealing at 750–1000 °C for one hour was sufficient to achieve the desired phase while maintaining the material’s sub-micrometer scale. Rietveld analysis of X-Ray diffraction data demonstrated that the crystal volume increases with Y doping. At the same time, with high Y incorporation, a segregation of the YPO₄ phase was observed in addition to the desired LATP phase. Another impurity phase, LiTiOPO₄, was observed besides YPO₄ and, with higher calcination temperature (1000 °C), the phase fraction for both impurities also increased. The ionic conductivity increased with Y incorporation from 0.1 mS/cm at room temperature in the undoped sample to 0.84 mS/cm in the case of LAY0.1TP, which makes these materials—especially considering the comparatively low sintering temperature—highly interesting for applications in the field of solid-state batteries. Full article

The microwave dielectric properties of (1−x)Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃-x(Nd_1/2La_1/2)(Mg_(1+δ)1/2Ti_1/2)O₃ ((1−x)CYTO-xNLMTO) ceramics were investigated in this study. It was discovered that the addition of 1 wt% CuB₂O₄ effectively enhanced the densification and improved the microwave dielectric properties of (1−x)CYTO-xNLMTO, where δ = 0.02. The new ceramic systems of (1−x)CYTO-xNLMTO could achieve ultra-low loss and a high dielectric constant. The novel ceramic systems comprising (1−x)CYTO-xNLMTO exhibited remarkably low loss and a significantly high dielectric constant. Full article

For the first time, inductively coupled plasma mass spectrometry (ICP-MS) was developed for determining the target elemental composition of gadolinium–aluminum garnets with the varying composition Gd_3–xCe_xSc_yAl_5–yO₁₂, where x = 0.01–0.16 and y = 0.25–1.75. This fact has a fundamental importance for obtaining optical ceramics with predictable properties. Using the proposed acid mixture and temperature-time program, microwave digestion of these materials and complete transfer of the sample’s components into solution were possible. Moreover, we estimated the influence of the matrix composition, sample introduction system and collision cell on the limits of determination (LOD) of impurity elements by ICP-MS (Mg, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, La, Pr, Nd, Sm, Eu, Tb, Er, Ho, Tm, Yb, and Lu). It has been shown that the conditions of mass spectral analysis proposed in this work provide LOD of target analytes in the range of 1∙10⁻⁶–4.15∙10⁻³ wt.%. The accuracy of the obtained results has been confirmed by the added-found method and by analyzing samples with known chemical composition. The standard deviation of repeatability (S_r) of the developed technique lies in the range from 1 to 6%. The developed analysis method is characterized by sensitivity, robustness and multi-elementality. It has application potential for other optical and ceramic materials of similar composition. Full article

SiC multiphase ceramics were prepared via spark plasma sintering using AlN and TiB₂ as the second phase and Y₂O₃ as a sintering additive. The effects of TiB₂ content (10 vol.% and 20 vol.%) and sintering temperature (1900 °C to 2100 °C) on the phase composition, microstructure, and mechanical and tribological properties of SiC multiphase ceramics were investigated. The results showed that Y₂O₃ reacts with Al₂O₃ on the surface of AlN to form the intercrystalline phase Y₄Al₂O₉ (YAM), which promotes the densification of the multiphase ceramics. The highest density of SiC multiphase ceramics was achieved at 10 vol.% TiB₂ content. Moreover, TiB₂ and SiC exhibited good interfacial compatibility. In turn, a thin solid-solution layer (~50 nm) was formed by SiC and AlN at the interface. The periodic structure of SiC prevented the dislocation movement and inhibited the base plane slip. The most optimal mechanic characteristics (a density of 98.3%, hardness of 28 GPa, fracture toughness of 5.7 MPa·m^1/2, and bending strength of 553 MPa) were attained at the TiB₂ content of 10 vol.%. The specific wear rates of SiC multiphase ceramics were (4–8) × 10⁻⁵ mm³/N·m at 25 °C and 2.5 × 10⁻⁵ mm³/N·m at 600 °C. The wear mechanism changed from abrasion at 25 °C to a tribo-chemical reaction at 600 °C. Therefore, adding lubricious oxides of TiB₂ is beneficial for the improvement in wear resistance of SiC ceramics at 600 °C. Full article

In order to improve the mechanical properties of the wear-resistant layer of the hob cutter ring in shield construction, the influence of different composite matrix powders on the comprehensive performance of the cladding layer was investigated. In this study, TiC-reinforced Fe-Ni-based cladding layers with different matrix compositions were prepared on a modified H13 steel base material using plasma cladding (PC) technology. The matrix powders included Ni-based alloy powder, iron powder Y, and iron powder R. The two iron powders were mixed in different proportions, and then an equal amount of Ni-based alloy powder and TiC ceramic particles were added to form five kinds of composite cladding layer alloy powders. The cladding layers of five different matrices were obtained by cladding. The microstructure and mechanical properties of the composite cladding layer were studied using a metallographic microscope (OM), an X-ray diffractometer (XRD), a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), an electronic universal testing machine, an image processing microhardness tester, and an abrasive belt friction and wear testing machine. The results showed that the cladding layers of different samples had good metallurgical bonding with the base material. And the microstructure gradually refined from the bottom of the cladding layer to the top of the cladding layer. The cladding layer phases were mainly composed of Fe, FeO, TiC, FeNi, and CrNi. With the increase in the iron powder R ratio, the aggregation of alloy elements gradually alleviated. The ratio of iron powder R was increased from 1/10 to 2/5, the longitudinal shear strength between the cladding layer and the matrix was increased from 318 Mpa to 333 Mpa, and the transverse shear strength was increased from 303 Mpa to 342 Mpa. The hardness of the modified wear-resistant layer was better than that of the cladding layer without iron powder R, but the hardness of the cladding layer gradually decreased. After the modification of iron powder R, the wear resistance of the cladding layer was improved to varying degrees. When Y:R was 9:1, its wear resistance was the best, and the change trend of the wear resistance was consistent with that of hardness. The wear forms of different samples were adhesive wear and abrasive wear. And the height difference of the wear surface gradually increased with the improvement in wear resistance. Full article

In this study, a NiCr/YSZ coating was applied to a γ-TiAl surface using multi-arc ion plating technology to enhance its high-temperature performance and explore the mechanisms of high-temperature oxidation and thermal corrosion. The thermal corrosion properties of the γ-TiAl matrix and NiCr/YSZ coating were investigated at 850 °C and 950 °C using a constant-temperature corrosion test in a 75% Na₂SO₄ + 25% NaCl mixture. The results indicate that after 100 h, the thermal corrosion weight gain of the coating samples was 70.1 mg/cm² at 850 °C and 118.2 mg/cm² at 950 °C. At these temperatures, sulfide formation on the surface increases, leading to a loose and porous surface. After 100 h of high-temperature corrosion at 850 °C, the primary oxidation product on the surface of the coating was tetragonal-ZrO₂. At 950 °C, Y₂O₃, which mainly acts as a stabilizer in YSZ, reacted with Na₂SO₄, resulting in the continuous consumption of Y₂O₃. This reaction caused a substantial amount of tetragonal-ZrO₂ to transform into monoclinic-ZrO₂, altering the volume of the ceramic layer, which induced internal stress, crack propagation, and minor spallation. A continuous and dense internal thermally grown oxide (TGO) layer effectively impeded the diffusion of molten salt substances and oxygen, thereby significantly improving the thermal corrosion resistance of the thermal barrier coating. Full article

The upconversion response of Er³⁺ sensitized by Yb³⁺ in various crystalline hosts and illuminated with a laser light at around 980 nm revealed certain spectral shapes that are typical for each of the crystalline matrices containing the dopants. The purpose of this work was to measure the upconversion response of Er³⁺ as a dopant in Y₂TiO₅, sensitized by Yb³⁺, at different concentrations relative to the substituted Y³⁺ ion, and to reveal the subtleties of the mechanisms of the energy transfers between them and the lattice. Therefore, we synthesized Y₂TiO₅ ceramic samples doped with different concentrations of Er³⁺ and Yb³⁺, below 10% (mol), in order to minimize the distortion of the lattice. The oxide powders, obtained using the sol–gel method, as well as the ceramics were structurally and morphologically characterized using an X-ray diffraction analysis and scanning electron microscopy. When the ceramic samples were irradiated with an NIR laser light, it was found that, at a wavelength variation of only 2 nm of the incident radiation, from 973.5 nm to 975.5 nm, the upconversion spectra differed significantly. This nonlinearity is notable because it is not present in the case of other crystalline host matrices studied by us since the literature lacks information on this subject. We also correlated this effect with the simulated distribution of the average distances between Er³⁺ and Yb³⁺ ions in the host matrix. Full article

Defects such as interconnected pores and cracks can improve the abradability of ceramic-based abradable sealing coatings (ASCs) but may reduce the lifetime. Self-healing can potentially close cracks and transform interconnected pores into isolated ones through filling and sintering effects. Ti₃AlC₂ (TAC) was incorporated into LaMgAl₁₁O₁₉ (LMA) as both the self-healing agent and sintering aid, and plasma-sprayed LMA-based composite coatings were annealed at 1200 °C to assess their self-healing capabilities and then subjected to oxidation in air and corrosion in steam at 1300 °C to study their long-term stability. Results indicated that increasing TAC content significantly enhances self-healing effectiveness, evidenced by the closure of cracks and the isolation of pores. Oxidation and corrosion at 1300 °C led to significant grain growth and the formation of equiaxed grains with an aspect ratio of approximately 3, which may impair the toughening mechanism. Meanwhile, due to the preferential volatilization of Al in a steam environment, LTA decomposed into α-La_2/3TiO₃ and La₄Ti₃O₁₂ phases, and the accelerated mass transfer also resulted in grain coarsening. Interestingly, the L20T composite coating with a porosity of 32.17 ± 0.94% and a hardness of 74.88 ± 1.55 HR15Y showed great potential for abradable applications due to its stable phase composition and uniform pore distribution. Full article

As consumer electronics and industrial control systems continue to evolve, the operating temperature range of capacitors is gradually increasing. Barium titanate-based ceramic capacitors are widely used in the field of high dielectrics, so temperature-stable barium titanate-based dielectric materials have been a hot research topic in the field of dielectric ceramics. The construction of a core–shell structure by unequal doping is an effective way to obtain temperature-stable dielectric materials. At the same time, this structure retains part of the highly dielectric tetragonal phase, and materials with overall high dielectric constants can be obtained. In this work, we prepared BaTiO₃-xNaNbO₃-0.002Gd₂O₃ (x = 1.0–6.0 mol%) as well as BaTiO₃-0.05NaNbO₃-yGd₂O₃ (y = 0–0.30 mol%) dielectric ceramics. On the basis of high-electronic-bandgap NaNbO₃-modified BaTiO₃ dielectric ceramics, a core–shell structure with a larger proportion of core phase was obtained by further doping the amphiphilic rare-earth oxide Gd₂O₃. By designing this core–shell structure, the temperature stability range of capacitors can be expanded. At a doping level of 5.0 mol% NaNbO₃ and 0.20 mol% Gd₂O₃, the room temperature dielectric constant ε_r = 4266 and dielectric loss tan δ = 0.95% conforms to the X8R standard (from −55 °C to 150 °C, TCC < ±15%); volume resistivity ρ_v = 10,200 GΩ·cm and breakdown strength E_b = 13.5 kV/mm is attained in BaTiO₃-based ceramics. The system has excellent dielectric and insulating properties; it provides a new solution for temperature-stable dielectric ceramics. Full article

This paper describes the process to obtain ceramic nanotubes from titanium dioxide, alumina and yttrium oxide by a feasible, replicable and reliable technology, including three stages, starting from an electrospinning process of poly(methyl methacrylate) solutions. A minimum diameter of 0.3 μm was considered optimal for PMMA nanofibers in order to maintain the structural stability of covered fibers, which, after ceramic film deposition, leads to a fiber diameter of 0.5–0.6 μm. After a chemical and physical analysis of the stages of obtaining ceramic nanotubes, in all cases, uniform deposition of a ceramic film on PMMA fibers and, finally, a uniform structure of ceramic nanotubes were noted. The technological purpose was to use such nanotubes as ingredients in screen-printing inks for electrochemical sensors, because no study directly targeted the subject of ceramic nanotube applications for printed electronics to date. The printing technology was analyzed in terms of the ink deposition process, printed electrode roughness vs. type of ceramic nanotubes, derived inks, thermal curing of the electrodes and the conductivity of electrodes on different support (rigid and flexible) at different curing temperatures. The experimental inks containing ceramic nanotubes can be considered feasible for printed electronics, because they offer fast curing at low temperatures, reasonable conductivity vs. electrode length, good printability on both ceramic or plastic (flexible) supports and good adhesion to surface after curing. Full article

Investigating the microwave dielectric properties of ceramics prepared through the conventional solid-state route, such as x[(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02-(1−x)Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃, reveals notable characteristics. [(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02 shows a permittivity (ε_r) of approximately 20, a high quality factor (Q × f) ranging between 250,000 and 560,000 GHz, and a temperature coefficient of resonant frequency (τ_f) of approximately −65 ppm/°C. To enhance the temperature stability, Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃ featuring a τ_f value of +374 ppm/°C was incorporated into the [(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02 composition. τ_f demonstrated an increase with rising Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃ content, reaching zero at x = 0.95. A ceramic composition of 0.95[(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02-0.05Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃, incorporating 3wt.% BaCu(B₂O₅) as sintering aids, exhibited outstanding microwave dielectric properties: ε_r~22.5, Q × f~195,000 (at 9 GHz), and τ_f~0.1ppm/°C, with a sintering temperature at 950 °C. This material is proposed as a prospective candidate for 6G band components and GPS antennas. Full article

This work explores the impact of the sintering temperature and co-dopant contents on the microstructure and dielectric properties of (Y_0.5Nb_0.5)_xTi_1−xO₂ (0.025 ≤ x ≤ 0.10) ceramics synthesized by the solid state reaction method. The physical mechanism underlying the colossal electric permittivity was systematically investigated with experimental methods and first principles calculations. All specimens exhibited the characteristic tetragonal structure of rutile, besides secondary phases. A niobium- and yttrium-rich secondary phase emerged at the grain boundaries after heating at 1500 °C, changing the main sintering mechanism. The highest value of the electric permittivity (13499 @ 60 °C and 10 kHz) was obtained for (Y_0.5Nb_0.5)_0.05Ti_0.95O₂ sintered at 1480 °C, and the lowest dissipation factor (0.21@ 60 °C and 10 kHz) for (Y_0.5Nb_0.5)_0.1Ti_0.90O₂ sintered at 1500 °C. The dielectric properties of Y³⁺ and Nb⁵⁺ co-doped TiO₂ are attributed to the internal barrier layer capacitance (IBLC) and electron-pinned dipole defect (EPDD) mechanisms. Full article

The paper reports on effect of grain-growth inhibitors MgO, Y₂O₃ and MnCO₃ as well as Ca modification on the microstructure, dielectric, ferroelectric and electrocaloric (EC) properties of Ba_0.82Sr_0.18Sn_0.065Ti_0.935O₃ (BSSnT). Furthermore, the effects of the sintering time and temperature on the microstructure and the electrical properties of the most promising material system Ba_0.62Ca_0.20Sr_0.18Sn_0.065Ti_0.935O₃ (BCSSnT-20) are investigated. Additions of MgO (x_MgO = 1%), Y₂O₃ (x_Y2O3 = 0.25%) and MnCO₃ (x_MnCO3 = 1%) significantly decreased the mean grain size of BSSnT to 0.4 µm, 0.8 µm and 0.4 µm, respectively. Ba_0.62Ca_0.20Sr_0.18Sn_0.065Ti_0.935O₃ (BCSSnT-20) gained a homogeneous fine-grained microstructure with an average grain size of 1.5 µm, leading to a maximum electrocaloric temperature change |ΔT_EC| of 0.49 K at 40 °C with a broad peak of |ΔT_EC| > 0.33 K in the temperature range from 10 °C to 75 °C under an electric field change of 5 V µm⁻¹. By increasing the sintering temperature of BCSSnT-20 from 1350 °C to 1425 °C, the grain size increased from 1.5 µm to 7.3 µm and the maximum electrocaloric temperature change |ΔT_EC| increased from 0.15 K at 35 °C to 0.37 K at 20 °C under an electric field change of 2 V µm⁻¹. Our results show that under all investigated material systems, BCSSnT-20 is the most promising candidate for future application in multilayer ceramic (MLC) components for EC cooling devices. Full article