Bi₂O₃ was investigated in the role of a modifier for BaTiO₃ powder synthesized in a water vapor atmosphere at 200 °C and 1.55 MPa. Modification was aimed at increasing the sinterability of the powder as well as improving the structural and dielectric properties of the obtained ceramics. The morphology and phase contents of the synthesized BaTiO₃ powder were controlled by the methods of SEM and XRD. Properties of pure and Bi-doped BaTiO₃ ceramics were comprehensively studied by XRD, SEM, dielectric spectroscopy, and standard approaches for density and mechanical strength determination. Doping with Bi₂O₃ favored BaTiO₃ ceramic densification and strengthening. The room-temperature dielectric constant and the loss tangent of Bi-doped BaTiO₃ were shown to stabilize within the frequency range of 20 Hz to 2 MHz compared to non-doped material. The drop of dielectric constant between room temperature and Curie point was significantly reduced after Bi₂O₃ addition to BaTiO₃. Bi₂O₃ appeared to be an effective modifier for BaTiO₃ ceramics produced from non-stoichiometric powder synthesized in water vapor.

In porous ceramics processing, the green body shaping technique largely determines the control of the final porous structure and material properties. The study is aimed at finding affordable approaches for the shaping of two different narrow-fraction fillers: F240 electro-corundum and hollow alumina microspheres. The results revealed the influence of accessible shaping techniques (semi-dry pressing, direct casting, and slip casting) on the structural and mechanical properties of porous alumina ceramics. The starting materials were characterized by XRD, SEM, EDX, and BET. The manufactured ceramics were studied in terms of microstructure, density, porosity, and flexural strength. Free stacking of the fillers’ particles during the direct and slip casting resulted in a higher porosity of ceramics compared with that of semi-dry pressing, while reducing its mechanical strength. Direct casting appeared preferable for ceramics with hollow microspheres because it maintained the integrity of the filler particles and preserved their inherent porosity in the ceramics. The optimal parameters for porous ceramics processing were determined as follows: pressing at 30 MPa and sintering at 1280–1320 °C with a bentonite content of 15 wt.%. In this case, the average density and open porosity of F240 samples reached 2.22 g cm⁻³ and 40.4%, while samples containing hollow microspheres reached 2.20 g cm⁻³ and 36.7%, respectively.

A facile and environmentally benign method for single-phase barium titanate synthesis in a water vapor medium was studied to reveal the mechanism of phase transformation of the initial simple oxide mixture and estimate the capability of the product to be used as a raw material for low-frequency dielectric ceramics. The composition and structure of the reactants’ mixture, treated in vapor at 130–150 °C as well as at 230 °C for various time periods, were investigated by means of XRD, SEM, TEM, EDX, and FTIR methods. The kinetics of the occurring phase transformation can be described using the Johnson–Mehl–Avrami–Erofeev equation. The reaction between the initial oxides was considered as a topochemical process with an apparent activation energy of 75–80 kJ mol⁻¹. A crucial role in this process belonged to the water vapor medium, which facilitated the generation of the reaction zone and the spreading inward of the solid particles. The synthesized tetragonal barium titanate powder (mean particle size of 135 nm) was sintered using a conventional technique at 1250 °C to obtain ceramics with grains of about 2 μm. Capacitance measurements identified a permittivity and dielectric loss factor of the ceramics that reached 3879 and 6.7 × 10⁻³, respectively, at 1 kHz and room temperature.

A facile and environmentally benign method for a single-phase barium titanate synthesis in water vapor medium was studied to reveal the mechanism of phase transformation of the initial simple oxides mixture and estimate the capability of the product to be used as a raw material for low-frequency dielectric ceramics. The composition and structure of the reaction mixture treated in vapor at 130…150 °C as well as 230 °C for various time were investigated by means of XRD, SEM, HRTEM, EDX, and FTIR methods. The kinetics of the occurring phase transformation was described by Johnson-Mehl-Avrami-Erofeev equation. The reaction between the initial oxides was considered as a topochemical process with an apparent activation energy of 74…80 kJ mol^-1. A crucial role in this process belonged to the water vapor medium, which facilitated the generation of the reaction zone and its spreading inward the solid particles. The synthesized tetragonal barium titanate powder (mean particle size of 135 ± 24 nm) was sintered by a conventional technique at 1250 °C to obtain ceramics with grains of about 2 μm. Capacitance measurements performed a dielectric constant and loss tangent of ceramics, which reached 3879 and 6.7 10^-3, respectively, at 1 kHz and room temperature.