Effect of the crystallinity of BaTiO3 powders prepared using the merker method on the properties of PTCR ceramics

Barium titanate powders differing in particle size (110-740 nm) were prepared by calcining barium titanyl oxalate precipitated by the Merker method. The powders were sintered to produce PTCR ceramics with the composition 100(Ba0.89Ca0.08Pb0.03)TiO3 + (TiO2)-Ti-0.8 + Y-0.7 + Mn-0.1 + (SiO2)-Si-2.5 and electrical properties of the ceramics were studied. The results demonstrate that improving the crystallinity of the barium titanate powder suppresses recrystallization of the ceramics and has a significant effect on their resistance ratio and electric strength. We found the optimal range of calcination temperatures (950-1000A degrees C) for barium titanyl oxalate which ensures the highest electric strength of thermistors with a resistance of 31 Omega. The average crystallite size of the parent barium titanate powder is similar to 250-320 nm.