Phenomenological Thermodynamic Theory for Pb(Zn1/3Nb2/3)O3-PbTiO3 Binary Solid Solution and Calculations for Phase Diagram, Dielectric Constants, Lattice Parameters and Piezoelectric Constants (New Estimation Method for Unknown Dielectric Stiffness Constants in Elastic Gibbs Free Energy for Binary System)

Abstract

Unknown dielectric stiffness constants in elastic Gibbs free energy for Pb(Zn1/3Nb2/3)O3 were estimated by fitting the calculated phase diagram with the experimental one for the Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) solid solution, and by considering the discontinuity of the dielectric constant at the rhombohedral-tetragonal morphotropic phase boundary in the (1-x)PZN-(x)PT system, x>0.105. The calculated PZN=PT phase diagram using the newly estimated values was in good agreement with the experimental PZN-PT one. The dielectric constants, lattice parameters and piezoelectric constants of the PZN-PT system could be calculated at a given composition and temperature. On comparison with experimental data, this method was found to be effective for material design.