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Phase relationships in the system Gd2O3-Al2O3-SiO2

1997; Elsevier BV; Volume: 257; Issue: 1-2 Linguagem: Inglês

10.1016/s0925-8388(96)03121-0

1873-4669

Uwe Kolitsch, H. J. Seifert, Fritz Aldinger,

Microwave Dielectric Ceramics Synthesis

Previously unknown phase equilibria in the system Gd2O3-Al2O3-SiO2 at 1400 and 1300 °C were determined using X-ray diffraction, SEM-EDX and EPMA. The following six quasibinary phases are observed: Gd4Al2O9, GdAlO3, Gd2SiO5, Gd9.33(SiO4)6O2, Gd2Si2O7 and 3Al2O3·2SiO2 (mullite). Additionally, there are two extended ternary solid solutions, Gd9.33+2x(Si1−xAlxO4)6O2 (with x=0−∼0.33) and Gd4Al2(1−x)Si2xO9+x (with x=0−∼0.3), that are based on the quasibinary phases Gd9.33(SiO4)6O2 and Gd4Al2O9, respectively. No quasiternary compound was detected. The ternary eutectic temperature was measured at 1306±5 °C by high-temperature STA and DSC. The results are compared with the scarce data available for other RE2O3-Al2O3-SiO2 (RE=rare earth element) systems.