Synthesis, structural and vibrational studies on mixed alkali metal gadolinium double tungstate, K1−xNaxGd(WO4)2

Mixed alkali double tungstates K1−xNaxGd(WO4)2 (KNGW) (0 ⩽⩽ x ⩽⩽ 1) were synthesized by solid state reaction using sodium doped monoclinic KGd(WO4)2 (KGW). Synthesized KNGW powders were characterized using powder X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and Raman analysis. DTA analysis confirms that the melting point of the KGW matrix increases from 1063 °C to 1255 °C with increasing sodium content. The Powder XRD analyses reveal that mixed phases were observed up to 40 wt.% of Na in the KGW matrix above that percentage there is domination of scheelite structure in the synthesized powder. Polyhedral type, bi-pyramidal shape and spheroid shape morphology was observed for KGW, NKGW and NGW powders respectively. The Raman analysis was carried out to understand the vibrational characteristic changes with mixing of sodium ions in the KGW matrix.

► Mixed alkali double tungstates K1-xNaxGd(WO4)2 (KNGW) (0 ⩽⩽ x ⩽⩽ 1) were synthesized by solid state reaction.
► DTA analysis confirmed that the melting point of KGW matrix increases from 1063 °C to 1255 °C with increasing sodium content.
► Powder XRD analyses revealed that mixed phases were observed up to 40 wt.% of Na in the KGW matrix.
► Raman analysis was carried out to understand the vibrational characteristic changes with mixing of sodium ions in KGW matrix.