THE FERROELECTRIC PHASE-TRANSITION IN PURE AND LIGHTLY DOPED BARIUM-TITANATE

The effect of light doping on the phase transition of the ferroelectric state in BaTiO3 has been studied using synchrotron radiation at Daresbury Laboratory, UK. Our results indicate that the presence of dilute impurities, which turn BaTiO3 from a wide band-gap intrinsic semiconductor into an extrinsic n-type semiconductor, changes the transition from a discontinuous to a continuous one, and produces large spatial variation in magnitude of the electric polarization in both the high- and low-temperature phases; these fluctuations were barely detectable in the pure, annealed material.