Structure-property relations in mesoscopic BaTiO3 and PbTiO3

Structure-property relations in mesoscopic BaTiO3 and PbTiO3 are reviewed f rom the standpoint of effects of crystallite size on intrinsic behavior usi ng the Landau-Ginzburg-Devonshire formalism. Experimental results based on x-ray diffractometry and quantitative calorimetry indicate that the critica l crystallite sizes (CCS) for the stabilization of the cubic paraelectric p hase in BaTiO3 and PbTiO3 are in the vicinity of 67 and 15 nm, respectively . The CCS scales inversely with the cubic-tetragonal transition temperature (Ttr). The depression in Ttr in PbTiO3 is -15 (C with decreasing crystalli te size (CS). A decrease in Ttr for BaTiO3 was not observed. Both systems p reserve their first order phase transformation characteristics with reduced CS. Electrostrictive coefficients were determined as a function of CS and were found to exhibit a pronounced increase with decreasing CS. The increas e in the electrostrictive coefficients offsets the decrease in spontaneous polarization and results in an increase in piezoelectric moduli suggesting that strong piezoelectric activity could indeed be observed in the mesoscop ic size range.