Synthesis and characterisation of chromium lutetium gallium garnet solid solution

The chromium lutetium gallium garnet system has been studied. Samples with 2xCaOxCr2O3(3 − 2x)Lu2O35Ga2O3 (x = 0.025, 0.05, 0.075, 0.1, 0.2 and 0.3,) and xCr2O3(3 − x)Lu2O35Ga2O3 (x = 0, 0.05, 0.075 and 0.3) compositions have been prepared in Ca,Cr:LGG and Cr:LGG systems, respectively. Samples were prepared by ceramic method, fired at 1250 °C/6 h and characterised by XRD, lattice parameters, UV-vis-NIR spectroscopy, CIE L*a*b* measurements and SEM/EDX. Results indicate that Ca,Cr:LGG and Cr:LGG solid solutions are obtained. In Cr:LGG system only Cr(III) is stabilised in octahedral positions substituting for Lu(III) and Ga(III). Both Cr(III) and Cr(IV) are present in Ca,Cr:LGG. The calcium is a charge compensator to stabilise Cr(IV) and this is the predominant oxidation state up to x = 0.075 composition. From this composition, Cr(III) becomes more stabilised in garnet lattice. Cr(IV) occupies generally tetrahedral and dodecahedral sites substituting for Ga(III) and Lu(III), while Cr(III) is in octahedral site substituting for Ga(III).