Influence of sintering temperature on microstructure of Na0.5Bi0.5TiO3 ceramics

Impact of Thermal Treatment on the Surface of Na0.5Bi0.5TiO3-Based Ceramics

“…Increasing the size of TiO 2 inclusions could mean that this process occurs mainly at TiO 2 and NBT-Eu interfaces. It seems that the small inclusion concentration observed at low thermal treatment temperatures characterizes the concentration of TiO 2 in the bulk of the ceramics [25], which is not related to thermal treatment. These inclusions could be considered as seeds, which grow if thermal treatment at increased temperatures is applied.…”

“…These inclusions could be considered as seeds, which grow if thermal treatment at increased temperatures is applied. At the same time, such a kind of NBT decomposition is possible only from a surface layer, while the concentration of TiO 2 inclusions in the bulk does not increase upon increasing sintering temperature [25]. This reflects significantly different conditions between the surface and the bulk of the ceramics with respect to Na and Bi volatilization-where, instead of increasing TiO 2 inclusion concentration, only the formation of large pores is observed at high sintering temperatures [25].…”

“…At the same time, such a kind of NBT decomposition is possible only from a surface layer, while the concentration of TiO 2 inclusions in the bulk does not increase upon increasing sintering temperature [25]. This reflects significantly different conditions between the surface and the bulk of the ceramics with respect to Na and Bi volatilization-where, instead of increasing TiO 2 inclusion concentration, only the formation of large pores is observed at high sintering temperatures [25]. This difference becomes understandable in the context of the present results; as a result of Na/Bi evaporation from the surface layer at high temperatures, the decomposition of NBT takes place instead of generating A-sublattice vacancies, and these elements in the bulk of the ceramics remain captured.…”

“…As it follows from the obtained SEM micrographs, the grain size on the surface in Region III obviously increases. It is known that increasing sintering temperature induces an increase in the grain size of the whole ceramic [25]. Therefore, when analysing the role of thermal treatment temperature in the grain size distribution on the surface, the impact of thermal treatment temperature on the grain size in the bulk of the ceramics cannot be excluded.…”

Composition and microstructure of Na0.5Bi0.5TiO3 ceramics with excess Bi

“…They are observed also in NBT compositions with excess and deficiency of Na in the raw chemicals (Na 0.52 Bi 0.50 TiO 3 and Na 0.49 Bi 0.5 TiO 3 ). This allows us to assume that: only deficiency of Bi is responsible for the appearance of TiO 2 . even in NBT composition, produced from stoichiometric ratios of the raw chemicals, only deficiency of Bi is responsible for the appearance of NaBiTi 6 O 14 and finally TiO 2 18 …”