Thermal behavior of germanates with olivine structure

A series of germanates with olivine structure: Me2GeO4 (Me = Mg, Ca); Li2MeGeO4 (Me = Mg, Zn); LiMeGeO4 (Me = Sc, In, Y), and the compound Li4GeO4 were obtained by solid-state synthesis. Their thermal behavior was studied from the viewpoint of the possibilities of growing single crystals as matrices doped with Cr4+ for lasers. By means of X-ray and DTA/TG analysis data are obtained about the melting temperatures, type of melting (with or without decomposition), the substances during melting with decomposition, as well as the temperatures of the polymorphic transitions for some of the germanates. Most of the data reported in this work are novel. It is found that owing to the rather high melting temperatures and the decomposition or polymorphic transitions during the melting, the germanates with olivine structure do not allow single crystal growth from their own melts, but the flux method from appropriate high-temperature solutions should be applied.