Synthesis and characterization of BaTi1-xSnxO3 powders and multilayered ceramic materials

BaTi1-xSnxO3 (BTS) powders, with x ranging from 0 to 0.15, were synthesized by solid-state reaction technique. Physical characteristics of synthesized BTS powders and sintered BTS ceramics were examined: average particle size, particle size distribution, average agglomerate size, morphology of synthesized BTS powders; crystal symmetry, unit cell parameters, temperature of phase transition, densification during sintering, density and microstructure of sintered ceramics, also, dielectric permittivity, coefficient of thermal expansion, remanent polarization and coercitive field, grain (bulk) and grain boundary resistivity. It was found that changing of tin content in BTS samples induced changes of their physical characteristics. The increase of tin content in BTS sintered materials led to decreasing of: tetragonality, percent of shrinkage during sintering and density of sintered materials, Curie temperature, remanent polarization, coercitive field, as well as decreasing of grain boundary resistivity. Also, there was increasing of: unit cell volume, porosity, and dielectric permittivity with increasing of tin content in sintered BTS materials. After detailed examination of the sintered BTS materials characteristics, BTS FGMs were prepared with variety of layeres number (from 2 to 6) and tin content within layeres. After sintering, BTS FGMs with different tin concentration gradient were formed. Shrinkages during sintering of BTS FGMs were examined, as well as their microstructure, tin content in cross section, and electrical characteristics. BTS FGMs show very complex behavior during sintering, which is influenced by Sn4+ diffusion through FGM layers. The diffusion of cations depends on the number and thickness of the layers, starting tin content in each layer, and also, on the heating rate during non-isothermal sintering. Even though the content gradient existed in the examined BTS FGMs and each of the layers exhibited different percent of shrinkage, no cracks or delamination were noticed in the samples after the sintering. Small degree of distortion is noticed in multilayered samples with graded (not continual) changes of tin content. Furthermore, it is noticed that multilayer BTS ceramics have a broadened peak of maximum permittivity εrmax, i.e. have a relatively high dielectric constant in a wide temperature range. This effect is clearly expressed in FGMs with more layers, and with continual changes of tin content in cross section. It was found that dielect