Preparation, structural and spectroscopic study of sol-gel-synthesized $$\hbox {Cr}^{3+}$$ Cr 3 + : $$\hbox {Al}_{2}\hbox {O}_{3}$$ Al 2 O 3 powder

Chromium-doped $$\alpha$$ - $$\hbox {Al}_{2}\hbox {O}_{3}$$ powder was synthesized by a modified sol–gel method using poly(vinyl alcohol) aqueous solutions and metal nitrate precursors. The synthesis process is simple, is of low cost and produced final crystals with cubic shape as confirmed by X-ray diffraction. The morphology of the samples verified by scanning electron microscopy showed slabs with thickness below 1  $$\upmu {\mathrm{m}}$$ , formed by interconnected long grains of typical thickness of around 200  $${\mathrm{nm}}$$ , showing growth of the grains as followed by thermogravimetric analysis. Luminescence characteristics of $$\hbox {Cr}^{3+}$$ were detected and analyzed as a function of the concentration of chromium using photoacoustic and photoluminescence spectroscopies.