Inorganics

Twelve nominal ABO₃ compositions, where A = La, Y, Lu and B = Al, Ga, Sc, In, were synthesized by the sol-gel method and annealed at 700–1300 °C. The phase formation behavior was evaluated using tolerance factor calculations, XRD, Rietveld refinement, FTIR, SEM, SEM-EDX, and ICP-OES analysis. La-based compounds showed the highest tendency to form perovskite phases, while Y-based samples revealed strongest phase competition, and Lu-based materials mainly formed non-perovskite structures. LuScO₃ and LuInO₃ have a cubic bixbyite-type structure, whereas LuAlO₃ and LuGaO₃ formed garnet and Lu₂O₃ oxide-containing mixtures. The FTIR results confirmed the formation of metal–oxygen bonds during annealing, while SEM revealed agglomerated and porous powders with composition-dependent differences in apparent morphological feature size. SEM-EDX mapping revealed homogeneous elemental distributions, while ICP-OES confirmed that the A/B cation ratios remained close to the nominal ABO₃ stoichiometry, suggesting that the secondary phase formation was mainly related to phase stability rather than deviation in composition.

Rare earth silicate materials received growing attention in recent years, driven by their potential for use in thermal/environmental barrier coatings and for scintillation applications for gamma-ray and X-ray detectors. $R_2$SiO₅, R₂Si₂O₇ and $R_{4.67}$(SiO₄)₃O (where R = Dy, Ho and Er) have been prepared by the conventional solid-state synthesis method. Through a systematic study, we have optimized the synthesis conditions, from the choice of the precursor to the optimal temperature profile for the chemical reaction. We demonstrate that, despite an overlap of the thermal stability ranges of different rare earth silicate compounds and their polymorphs in the phase diagrams of the R-Si-O systems, it is feasible to prepare polycrystalline materials with a high yield of the target phase. Moreover, we offer our perspectives into the kinetics of the different chemical phases within the rare earth silicate systems. We show that the chemical reactions are faster when employing the $\alpha$-cristobalite polymorph of SiO₂ as a precursor, and we establish a reliable and reproducible solid-state synthesis protocol for Dy₂SiO₅, Ho₂SiO₅, Er₂SiO₅, Ho₂Si₂O₇, Er₂Si₂O₇, Dy_4.67(SiO₄)₃O and Ho_4.67(SiO₄)₃O. We reveal the results of our efforts to optimize the synthesis conditions for the preparation of all Dy-, Ho-, and Er-based silicate phases, which can be extended to other members of the rare earth silicate families, enabling the synthesis of bulk materials with improved phase purity.

Piezoelectric semiconductor PN junctions hold considerable promise for self-powered sensing, flexible electronics, energy harvesting, photodetection, and multifunctional micro/nanodevices. A local temperature change couples the built-in electrical response of the PN doping interface with the thermally induced response at the boundaries of the heated region, thereby modifying the electric potential, electric field, electric displacement, and carrier distributions near the junction. To elucidate this coupling mechanism, a one-dimensional three-interface analytical model is developed for a piezoelectric semiconductor PN junction subjected to a local temperature change. The fiber is divided into cold P-type, heated P-type, heated N-type, and cold N-type regions, and the coupled response is determined using piecewise analytical solutions together with open-circuit end conditions, interface continuity conditions, global carrier-conservation constraints, and reference-point conditions. Within a linear small-perturbation framework for an ideal zero-thickness homojunction, numerical results show that the PN doping interface governs the baseline distributions of the built-in potential and electric field, whereas the temperature interfaces generate additional electric fields through temperature-induced electric-displacement compensation, leading to localized redistribution of holes and electrons. For the baseline ZnO case with a 0.5 K temperature increment, the potential span is 9.124 mV, the peak electric-field magnitude is 48.43 kV m⁻¹, and the maximum carrier perturbation is 0.180 of its regional reference concentration. Independent Galerkin finite-element calculations agree with the analytical solution, with a maximum normalized discrepancy of 0.553% on the finest mesh. The temperature-change amplitude, heated-region half-width, reference carrier-concentration level, P/N doping asymmetry, effective dielectric constant, and effective thermal electric-displacement coefficient modify the potential transition, electric-field peaks, and carrier-screening range near the junction. These results reveal the coupled interaction between the local temperature interfaces and the PN doping interface and provide a theoretical basis for thermally regulating piezoelectric semiconductor junction devices under localized thermal loading.