Acta Crystallographica Section B

Structural Science

Volume 55, Part 1 (February 1999)

Acta Cryst. (1999). B55, 8-16    [doi:10.1107/S0108768198005758]

Temperature-dependent neutron powder diffraction evidence for splitting of the cationic sites in ferroelectric PbHf_0.4Ti_0.6O₃

C. Muller, J.-L. Baudour, V. Madigou, F. Bouree, J.-M. Kiat, C. Favotto and M. Roubin

Abstract: Temperature-dependent neutron powder diffraction experiments (diffractometer 3T2-LLB, Saclay, France, = 1.227  Å) have been performed on the perovskite-like lead hafnate titanate PbHf_0.4Ti_0.6O₃. This compound belongs to the solid solution denoted PHT, which derives from the well known ferroelectric PZT series. It exhibits a ferroelectric-to-paraelectric phase transition around 620  K, between the low-temperature tetragonal phase and the high-temperature cubic phase. The tetragonal structure of the ferroelectric phase has been refined at 10 and 300  K using a Rietveld-type method: space group P4mm with Z = 1; a_t = 3.999  (1), c_t = 4.120  (1)  Å, c/a = 1.030, V = 65.89  Å³ at 10  K; a_t = 4.012  (1) and c_t = 4.100  (1)  Å, c/a = 1.022, V = 65.99  Å³ at 300  K. The cubic structure of the paraelectric phase has also been refined at 720  K: space group Pm3m, Z = 1, a_c = 4.046  (1)  Å, V = 66.23  Å³. Cation displacements and oxygen-octahedra elongations have been observed as a function of temperature. Evidence for peculiar behaviour associated with the relative shifts of the Hf and Ti atoms (thought until now to be on the same crystallographic site) was found through an anomaly of the mean-square atomic displacements of the Hf/Ti pseudo-nucleus. The PDF Nos for PbHf_0.4Ti_0.6O₃ are 48-49-9 and 48-49-10.

Online 1 February 1999

	Rietveld powder data file (CIF format) (30.1 kbytes) Contains datablock 1
	Rietveld powder data file (CIF format) (28.8 kbytes) Contains datablock 2
	Rietveld powder data file (CIF format) (30.1 kbytes) Contains datablock 3

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