Synthesis and Photoluminescent Property of $\text{MgO:Cr}^{3+}$ Powders

Abstract

MgO:Cr³⁺ powders with different dopant contents have been synthesized by sol-gel method using the following precursors: magnesium nitrate (Mg(NO₃)₂), chrome nitrate (Cr(NO$_3$)$_3$), and citric acid. The effect of the Cr$^{3+}$ concentration and heat-treating temperature on structural and optical properties of the synthesized samples has been studied. For the samples with the low Cr³⁺-dopant concentrations or low heat-treating temperature, the photoluminescent (PL) spectra consist of sharp lines assigned to the $^2$E $\to$ $^4$A$_2$ transition of ions Cr³⁺ in perfect octahedral symmetry sites. But for the samples with the high Cr$^{3+}$-dopant concentrations and undergone high heat-treating temperature, the PL spectra appear a broad emission bands, which is assigned to the $^4$T$_1\to ^4$A$_2$ transitions within the Cr$^{3+}$ ions in the MgO orthorhombic symmetry crystal field.