Neutron scattering study of PbMg₁/₃Ta₂/₃O₃ and BaMg₁/₃Ta₂/₃O₃ complex perovskites
Gvasaliya, S. N. · Roessli, B. · Sheptyakov, D. · Lushnikov, S. G. · Shaplygina, T. A.
Original · EN
Neutron scattering investigations were carried out in PbMg₁/₃Ta₂/₃O₃ and BaMg₁/₃Ta₂/₃O₃ complex perovskites. The crystal structure of both compounds does not show any phase transition in the temperature range 1.5 -- 730 K. Whereas the temperature dependence of the lattice parameter of BaMg₁/₃Ta₂/₃O₃ follows the classical expectations, the lattice parameter of relaxor ferroelectric PbMg₁/₃Ta₂/₃O₃ exhibits anomalies. One of these anomalies is observed in the same temperature range as the peak in the dielectric susceptibility. We find that in PbMg₁/₃Ta₂/₃O₃, lead ions are displaced from the ideal positions in the perovskite structure at all temperatures. Consequently short-range order is present. This induces strong diffuse scattering with an anisotropic shape in wavevector space. The temperature dependences of the diffuse neutron scattering intensity and of the amplitude of the lead displacements are similar.
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