Cr doped Ca2GeO4, Ca5Ge3O11 and Li2CaGeO4 single crystals grown by the flux method

Pure and Cr doped Ca2GeO4, Ca5Ge3O11 and Li2CaGeO4 single crystals were grown by the flux method. The Ca2GeO4 crystals were grown at significantly more proper conditions than used up to now, while Ca5Ge3O11 and Li2CaGeO4 single crystals were grown for the first time. The macroscopic defects are characterized and discussed in relation to the growth conditions. The distribution coefficients of Cr were established being very different for the three crystals. EPR investigation shows that as in the case of Ca2GeO4, in Ca5Ge3O11 and Li2CaGeO4 the Cr occupied the tetrahedral position. The Cr doped crystals show broad band emissions from 1000 to 1600 nm. The dependence of the integrated intensity of emission on the Cr concentration in the crystals is discussed.