Enthalpies of foramtion of lead zirconate titanate (PZT) solid solutions

摘要

The formation energetics and heats of mixing of lead zirconate titanate (PZT) PbZr_xTi_(1-x)O_3 solid solutions have been investigated using high-temperature oxide melt solution calorimetry. While the heat content (H_(973)-H_(298)) is almost constant (80-82 kJ/mol) for x = 0.15-1.0, its value for PbTiO_x(x=0.0) is larger (86.15 +- 0.55 kJ/mol). Linear variation in the enthalpy of drop solution, #DELTA#H_(d3) and the enthalpy of formation from the oxides, #DELTA#H_(f,ox) (298 K), is observed in the tetragonal region (0orthorhombic) as 24.0 +- 3.9 kJ/mol. An extrapolation from the rhombohedral region gives 33.3 +- 3.6 kJ/mol for #DELTA#H of the virtual transition PbZro_3 (orthorhombic or rhombohedral -> tetragonal). The transition enthalpy between orthorhombic and rhombohedral PbZrO_3 is zero within experimental error. The enthalpy of formation from the oxides, #DELTA#H_(f,ox) (298 K), varies from -36.7 +- 2.7 kJ/mol for PbTiO_3 to 0.7 +- 4.3 kJ/mol for PbZrO_3. The #DELTA#H_(f,ox) (973 K) values agree with previously reported #DELTA#H_(f,ox) values measured in alkall borate solvent at 1073 K. Fitting #DELTA#H_(mix)(973 K) to a regular solution model yields an interaction parameter, W,of 39.8 +- 4.6 kJ/mol.However, structural complexity makes the regular solution model only a crude physical description.