Synthesis of New Sr3RE2(Ge3O9)2 (RE=La, Y) cyclogermanates by liquid-phase precursor methods

New cyclogermanates Sr 3 RE 2 (Ge 3 O 9 ) 2 ( RE =La, Y) with Ca 3 Y 2 (Si 3 O 9 ) 2 cyclosilicate structure type have been prepared by two liquid-phase precursor routes: the citrate and the Pechini methods. The phase composition, morphology and optical properties of the intermediate and final products have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance spectroscopy (DRS). The thermogravimetric (TGA) and differential thermal analyses (DTA) were used to study the thermal decomposition of the precursors. The powder XRD measurements indicate that the phase formation of Sr 3 RE 2 (Ge 3 O 9 ) 2 ( RE =La, Y) (S.G. C 2 /c , Z=4) takes place after 20 h annealing at 800 °C. The DRS data revealed that the cyclogermanates are promising optical hosts.