Particle-size-induced diffuse phase transition in the fine-particle barium titanate porcelains

The effect of particle size on the ferroelectric transition in fine-particle BaTiO3 porcelain produced by the inorganic sol-gel method was investigated. The phase transition was measured by dielectric properties, variable temperature x-ray diffraction, and differential scanning calorimetry (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 to 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.