A study of structures and order parameters in antiferroelectric PbHfO3 by synchrotron radiation

We present structures of PbHfO3 between 100 and 525 K analyzed by a Rietveld method using synchrotron radiation. Spontaneous strain of a perovskite sublattice, could be excellently expressed by a conventional phenomenological theory in a room-temperature antiferroelectric phase. Pb shifts along the a-axis and the square root of the spontaneous strain showed similar dependence on temperature as expected from the theory below 200 K, while one of the shifts showed a slight deviation at high temperature. Disordered arrangement of Pb atoms in the Cubic phase was found as in the cubic phase of PbZrO3, though the direction of the disorder in PbHfO3 was not so obvious as that in PbZrO3.