Crystal growth of compounds in the MgO-Nb205 binary system

Abstract

In the system MgO-Nb2O5, four compounds are known to exist. MgNb206 is congruently melting at 1570°C while the compounds (Mg,Nb)O2.42, Mg5Nb4OI5 and Mg4Nb209 decompose peritectically at 1445, 1580 and 1730°C, respectively. Small crystals of all four compounds were grown by the laser-heated pedestal growth (LHPG) method. The Nb205-rich compounds showed some tendency to partial reduction of Nb5+ even when grown in an 02 atmosphere, resulting in a bluish-black color in the as-grown crystals. In contrast to this, the MgO-rich compounds were colorless, even though they were grown at higher temperatures. We also report the luminescence and Raman spectra of the four compounds.