Growth and Characterization of Pure Gd-Heptamolybdate and Mixed Gd-Ba-Molybdate Crystals

Abstract

The growth of pure Gd- and mixed Gd-Ba-molybdate crystals, bearing the stoichiometric composition Gd 2 Mo 7 O 24 · x H 2 O and Gd 2 Ba 24 Mo 42 O 153, is achieved by the gel technique, using the system RCl 3 −(NH 4 ) 6 Mo 7 O 24 −NH 4 NO 3 −HNO 3 −Na 2 SiO 3 (where R = Gd, Gd:Ba). Addition of Ba in the lattice of pure Gd-heptamolybdate influences the morphological developments of grown crystals. While pure Gd-heptamolybdate assumes a spherulitic morphology under all conditions of growth, the addition of Ba modifies the morphology of mixed crystals drastically and develops them as well-facetted pyramidal twinned crystals. The mixed crystals do not carry any water of hydration and are thermally more stable as compared to pure Gd-heptamolybdate carrying water of hydration.