Structural and spectroscopic characterization of Al2−x Cr x O3 powders obtained by polymeric precursor method

Al2O3 and Al2−xCrxO3 (x = 0.01, 0.02 and 0.04) powders have been synthesized by the polymeric precursors method. A study of the structural evolution of crystalline phases corresponding to the obtained powders was accomplished through X-Ray Diffraction and UV-vis spectroscopy (reflectance spectra and CIEL*a*b* color data). The obtained results allow to identify the γ-Al2O3 to α-Al2O3 phase transition. The single-phase α-Al2O3 powder was obtained after heat treatment at 1050 °C for 2 h. The results show that the green to red color transition and ruby luminescence lines observed for the powders of Al2−xCrxO3 are related to the γ to α-Al2O3 phase transition and the temperature and time range for such transition depends on the chromium content.