Re-Examination of the Structure of Sr2(MgTe)O6 Double Perovskite

Rick Ubic, Boise State University
Steven Letourneau, Boise State University
S. Thomas, National Institute for Interdisciplinary Science and Technology (CSIR)
G. Subodh, Univerisität Stuttgart
M. T. Sebastian, National Institute for Interdisciplinary Science and Technology (CSIR)

Abstract

Sr(2)MgTeO(6) powders and pellets were prepared by a solid-state ceramic route. The structure and microstructure were investigated using x-ray diffraction, transmission electron microscopy, and scanning electron microscopy methods. A structural inconsistency was discovered between the pseudocubic tetragonal structure (14/m) and the pseudotetragonal monoclinic P2(1)/n structure of Ca(2)MgTeO(6), both of which have previously been reported. Rather than undergoing an antiphase-to-in-phase tilt transition along the long axis, a more probable untilted-to-in-phase tilt transition was found, lowering the symmetry of Sr(2)MgTeO(6) to monoclinic, I2/m. Additionally, slight breaks in the fourfold symmetry expected in the < 001 > (tetragonal) orientations observed in electron diffraction patterns support the lowering of symmetry.