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Abstract: Ceramics based on LnTiTaO6 (Ln =La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were prepared using a conventional solid-state ceramic route. The structure and microstructure of the samples were analyzed using scanning electron microscopy, synchrotron X-ray powder diffraction and neutron diffraction techniques. The unit cell volume of the ceramics decreased with a decrease in ionic radius of the rare-earth ions until a phase change was seen at Ho where the space group changed from Pnma to Pbcn. The results confirmed that the boundary of the aeschynite to euxenite phase change that lies between DyTiTaO6 and HoTiTaO6 and demonstrate that this is a result of distortion of the channels in the aeschynite structure. [Copyright &y& Elsevier]

The β -phase of Au 7 Cu 5 Al 4 undergoes a reversible shape-memory phase transformation for which several conflicting martensite phases have been reported. Here we show the significance of the cooling temperature used to obtain the martensite. If Au 7 Cu 5 Al 4 is cooled from the parent phase condition to cryogenic temperatures, e.g. below 200 K, the martensitic phase is orthorhombic (space group Pcmn , a = 4.4841 Å, b = 5.8996 Å, c = 17.8130 Å); however, when this composition is cooled to only ∼260 K it will in general consist of a mixture of orthorhombic and monoclinic phase (the latter has space group P 2 1 / m , a = 4.4742 Å, b = 5.9265 Å, c = 13.3370 Å, β = 91.425°). In contrast, a sample with decreased Al content (Au 7 Cu 5.7 Al 3.3 ) transforms fully to monoclinic phase if cooled to ∼260 K. [ABSTRACT FROM AUTHOR]