Statistical Mechanics of Cation Ordering and Lattice Dynamics Calculations of Disordered and Some Ordered Phases of PbZrxTi1-xO3.

The effective Hamiltonian was obtained and thermodynamic properties of B-cation ordering in solid solution of PZT were studied by Monte-Carlo method. The temperatures of B-cation ordering phase transitions Tc ∼⃒ 180 K and Tc∼⃒ 250 K were determined for concentrations x = 1/3 and x = 1/2, respectively. This temperatures are essentially lower than melting temperature (Tm ∼⃒ 1200 K) of this compound and because of diffusion character of ordering process in alloy kinetics of such ordering at room temperatures is “frozen” and there is no the real phase transition to ordered phase that was observed experimentally. The lattice parameters, phonon dispersions, dielectric constant, Born effective charges for some ordered and fully disordered PbZr1-xTixO3 for 0 ≤ x ≤ 1 were calculated. The calculation was performed using the nonparametric generalized Gordon-Kim model with regard to the deformability, dipole and quadropole polarizabilities of ions, for disordered solid solution in framework of the used virtual crystal approximation. [ABSTRACT FROM AUTHOR]