Crystal Structure And Properties Of New Compounds And Phase Relations In The Mgo-In₂O₃-B₂O₃System

ABSTRACT:Subsolidus phase relations of MgO-In2O3-B2O3system at two temperature ranges have been investigated mainly by solid-state reaction and powder X-ray diffraction method. Three new ternary borate compounds:MgInBO4, MgIn7/8B7/8O29/8and Mg2InBO5were identified for the first time. MgIn7/8B7/8O29/8is supposed to be the ideal low-temperature form of MgInBO. When MgIn7/8B7/8CO29/8exists, there are ten definite three-phase regions. However, there are eight three-phase regions at the high temperature range. Besides MgInBO4and Mg2InBO5, there is still a metastable compound which needs to be confirmed.The crystal structure of MgInBO4was refined via Rietveld method. MgInBO4, which crystallizes in the Pnma space group, belongs to the warwickite family. MgIn7/8B7/8O29/8, whose crystal structure was solved ab initio, crystallizes in the P121/n1space group. Mixed occupancies between Mg and In atoms exist in their structures. Both the structure of MgInBO4and MgIn7/8B7/8O29/8contain InO6, MgO6octahedra, and isolated BO3triangles. The UV-vis excited fluorescence spectra of Eu3+and Tb3+in the matrix of MgInBO4and MgIn7/8B7/8O29/8show good luminescence properties, which indicates that they may have potential application in white LEDs and PDP.The crystal structure of; Mg2InBO5was also solved ab initio with powder diffraction date. Mg2InBO5belongs to the ludwigite family. It crystallizes in the Pbam space group and contains In/MgO6octahedra and isolated BO3triangles. BO3group was confirmed by infrared spectrum. The UV-vis diffuse reflectance spectrum of Mg2InBO5indicated it may be the promising optical-functional material in the future.