O-3 tilt and the Pb/(Zr/Ti) displacement order parameters in Zr-rich PbZr1-xTi(x)O(3) from 20 to 500 K

Neutron diffraction and dielectric data have been collected from a polycrystalline sample of PbZr1-xTixO3 (x=0.035) to determine the temperature dependence of the two-order parameters associated with the oxygen octahedral tilt and the Pbl(Zr/Ti) displacement, respectively, through the sequence of phase transitions F-RL-F-RH-P-C present in this mixed system. The weak coupling between tilt and polarization (displacements) is satisfactorily described within the framework of a two-order-parameters statistical theory in which the respective effective fields involve two higher-order terms in addition to a linear term.