Growth and the actual compositions of cation‐deficient sodium‐gadolinium molybdate single crystals

The concentration series of sodium‐gadolinium molybdate (NGM) crystals have been grown by Czochralski technique from stoichiometric Na${}_{0,5}$Gd${}_{0,5}$MoO${}_4$ melt, and from seven different nonstoichiometric melts in various atmospheres. The actual cation compositions of the crystals are measured by microprobe analysis. The location of the congruently melting composition is found for this compound, and the homogeneity field is evaluated. The unit cell parameters of the crystals have been calculated from X‐ray diffraction (XRD) analysis results. Hydrostatic densities of the crystals are measured. Based on these results, the actual molar weights of the samples are calculated that allows more precise determination of the crystals compositions. The studied crystals are shown to contain substantial sodium deficiency and excess of gadolinium compared to stoichiometry. The amount of cation vacancies occurs in both sublattices along with increase of Gd${}_2$O${}_3$/Na${}_2$O molar ratio in the crystals. (© 2020 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)