Particle-size effect on the ferroelectric phase transition in PbSc1/2Ta1/2O3 ceramics

The particle-size dependence on the ferroelectric phase transition in nanocrystalline PbSc1/2Ta1/2O3 ceramics has been investigated for particles in the 0.01–0.16 μm size range. The phase transition was monitored through measurement of the dielectric constant as a function of temperature, variable temperature x-ray diffraction, and differential scanning calorimetry. The c/a tetragonality ratio decreased monotonically with particle size, reducing to unity at 0 °C for particles ⩽0.053 μm in size. The ferroelectric transition temperature Tc decreased gradually and the phase transition became more diffuse in nature as the particle size decreased. Below a mean particle size of 0.02 μm there was no peak in either the dielectric constant or the differential scanning calorimetry curve as a function of temperature, even though variable temperature x-ray diffraction could detect tetragonality indicative of ferroelectric distortions at sufficiently low temperatures down to the smallest crystallite size of 0.01 μm.