The effect of composition, processing conditions, and irradiation, on lattice defects in spinel ceramics

The lattice defects in pure spinel ceramics MgO . nAl(2)O(3) were investigated as to their dependence on composition, temperature, and time duration of calcination in the course of synthesizing spinel powder. Defects were studied by optical methods measuring absorption and photo-, thermo-, and X-ray-stimulated luminescence. The variation of ceramic composition 0.98 less than or equal to n less than or equal to 1.02 leads to the formation of different absorption bands: at n < 1 absorption bands are present at a wavelength of 480 nm (2.6 eV) with Delta E = 0.75 eV; at n > 1 the band is at 620 nm (2.0 eV) with Delta E = 0.5 eV; and at n = 1 ceramics are transparent. In luminescence spectra, prominent bands were observed at 253, 370, and 520 nm. Variation of temperature of calcination in the range of 1150-1220 degrees C; duration of calcination of 0.5-2.0 h; and irradiation with X-rays, electrons, and neutrons cause changes in the relative intensities of the absorption and luminescence bands, which makes identifying the nature of lattice defects in spinel ceramics possible. (C) 1998 Elsevier Science B.V.