New pink ceramic pigment based on chromium (IV)-doped lutetium gallium garnet

Lutetium gallium garnet codoped with chromium and calcium (Ca,Cr:LGG) and lutetium gallium garnet with chromium as single dopant (Cr:LGG) have been studied. Samples with Ca x Cr x Lu 3−2 x Ga 5O 12 ( x = 0, 0.05, 0.10, 0.15, 0.2, 0.4, 0.6,) and Cr x Lu 3− x Ga 5O 12 ( x = 0.15 and 0.6) compositions were prepared by solid state reaction and the fired samples (1250 °C/6 h) were characterised by XRD, lattice parameters determination, UV–vis–NIR spectroscopy, CIE L* a* b* measurements and SEM/EDX. Moreover, the samples with calcium were tested as ceramic pigments in a conventional glaze matrix. In the Ca,Cr:LGG system solid solutions incorporating both Cr(III) and Cr(IV) ions were obtained. Cr(IV) occupies basically dodecahedral sites substituting for Lu (III) and is the predominant oxidation state up to x = 0.20 composition, giving a pink colouration in the ceramic glaze matrix. In the Cr:LGG system, only Cr(III) enters in solid solution occupying octahedral positions and producing green shades.