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Abstract: The reliability factors of a Rietveld X-ray powder refinement of PbCrO3 could be improved by considering the lead ion in a multi-minimum potential displaced from its special position. These studies coupled to EDX analysis show a certain lead deficiency. Electron diffraction and high-resolution electron microscopy reveal that the microstructure of this material is a rather complex perovskite superstructure that presents a compositional modulation, within a microdomain distribution. The proposed supercell is . [Copyright &y& Elsevier]

We have synthesized a new Bi 0.5 Pb 0. 5CrO 3 perovskite phase by means of a high pressure reaction at 70 kbar and 1000 °C. The distorted orthorhombic perovskite structure can be indexed in the space group Pnma with lattice parameters a =5.4768 (1) Å, b =7.7450 (2) Å, and c =5.4574 (1) Å at room temperature, but undergoes a structural phase transition and enters into a P 2 1 / m monoclinic distorted perovskite phase below 150 K with a =5.4173 (2), b =7.7286 (4) and c =5.4930 (3). The structural transition is coincident with the onset of magnetic interactions. At lower temperatures a weak ferromagnetic structure is evident related to antiferromagnetic Cr-spin canting and a spin-glass transition is observed at ≈40 K. The semiconducting-type electrical resistivity is relatively low, associated with Cr 3+ /Cr 4+ electron hopping, and shows considerable magneto-resistance (up to 15%). Due to the low resistivity the dielectric permittivity ε r could be determined only below T <80 K to be ≈300 and did not show any strong temperature-dependence. Ferroelectricity was not detected in the T -range investigated and no magnetocapacitance effects were observed. [ABSTRACT FROM AUTHOR]