Relationship between MPB and Emergence of Structural Boundary in Cubic Phase of Pb-Based Perovskite-Type Solid Solutions PZT and PZN-PT

抄録

High-energy synchrotron-radiation powder-diffraction experiments for PbZr1-xTixO3 (PZT: 0≦x≦1) and (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT: 0≦x≦0.3) have been performed to investigate the relationship between the structural features of the cubic phase at high temperatures and the morphotropic phase boundary (MPB) at low temperatures. Our precise Rietveld analyses for PZT and PZN-PT with various compositions have revealed that the Pb atom in the cubic phase is disordered around the cubic corner site, and the thermal motions abruptly change at the distinctive composition x ~ 0.5 for PZT and at x ~ 0.15 for PZN-PT, where MPB of each solid solution separates the tetragonal and rhombohedral phases at low temperatures. No anomalous change in thermal motions is detected for other atoms. Hence, we consider that the appearance of MPB is strongly related to the change in local environment around the Pb atom.