Phase diagram studies in the systems La2O3-SrO-MgO-Ga2O3 at 1350-1400°C in air with emphasis on Sr and Mg substituted LaGaO3

The ternary systems La2O3-SrO-Ga2O3, La2O3-MgO-Ga2O3, and the quaternary system La2O3-SrO-Ga2O3-MgO were studied at 1350-1400 degreesC in air with emphasis on the solid solubility of Sr and Mg in LaGaO3. In both ternary systems the solid solubility of Sr substituting for La and that of Mg substituting for Ga, respectively, is rather small. However, when Sr and Mg are present simultaneously, the solid solubility of Sr and Mg in LaGaO3 increases significantly. In addition, several phases of the quaternary system exhibit a pronounced variation of their La:Sr ratio and a high solid solubility of Mg, as for example LaSrGa3O7 and LaSrGaO4. The structure LaGaO3 containing Sr and Mg has been determined to be orthorhombic, space group Pbnm, a=5.53443 Angstrom, b=5.49523 Angstrom, and c=7.78320 Angstrom. In the quaternary system, extended four phase regions exist between LaGaO3, MgO and the La-Sr-Ga-O compounds. Quaternary phases were not observed. (C) 2001 Elsevier Science BY All rights reserved.