Original paper

Crystal structure and high temperature phase relations of monoclinic and orthorhombic pyroxene-compounds MnGeO3: a comparison

Redhammer, Günther J.; Vorberg, Christina; Tippelt, Gerold

Abstract

The pyroxene-type compound MnGeO3 crystallizes in both, the monoclinic C2/c and the orthorhombic Pbca modification in flux growth experiments using MnCl2. The structure of both forms was determined and refined at room temperature using single crystal X-ray diffraction data and compared, both among each other and with other MeGeO3 compounds (Me = Mg, Co and Fe). In solid state sintering and tempering experiments it is shown that between 800 °C and 1050 °C only the orthorhombic form is obtained, while at T > 1050 °C also monoclinic MnGeO3 is found, however, the total amount of the C2/c phase does not exceed 18(1) wt. %. During in situ X-ray diffraction measurements on a powdered sample from the flux growth experiment, a C2/c to Pbca phase transition takes place around 860 °C.

Keywords

clinopyroxeneorthopyroxenemngeo3single crystal structure analysisphase relationsphase transition