PARTICLE-SIZE-INDUCED DIFFUSE PHASE-TRANSITION IN THE FINE-PARTICLE BARIUM-TITANATE PORCELAINS

The effect of particle size on the ferroelectric transition in fine-pa rticle BaTiO3 porcelain produced by the inorganic sol-gel method was i nvestigated. The phase transition was measured by dielectric propertie s, variable temperature x-ray diffraction, and differential scanning c alorimetry (DSC). The tetragonal distortion of the unit cell decreases with size and vanishes at 0.037 mu m. The T-c decreases gradually but the transition becomes diffuse with a decrease in the size of 0.081 t o 0.040 mu m, below which there is no peak in the dielectric constant or DSC curve, though ferroelectric distortion (c/a) persists down to 0 .037 mu m.