Influence of growth atmosphere on Ca3TaGa3Si2O14 single crystals optical properties

Ca3TaGa3Si2O14 crystals were grown by the Czochralski technique in different atmospheres. Crystal grown in pure Ar was colourless and in N2+(1-3)%O2 - yellowish coloured. In the absorption spectra of yellowish CTGS we observed anisotropy: no significant absorption bands are observed in Z direction, but in X direction we observe absorption bands at 360 nm and at (470-480) nm. In case of colourless CTGS we observed extremely low intensity of the absorption band at ∼500 nm, in near UV we observed anisotropy of absorption and absorption band at ∼290 nm for X direction. Dichroism degree intensity is extremely low for these crystals, with maximum connected with coloration at 470 nm for yellow crystal and in case of colourless CTGS the main extrema are observed in near UV.