Synthesis and characterization of columbite type solid solution structured niobate Mg<sub>1−</sub><i><sub>x</sub></i>Ca<i><sub>x</sub></i>Nb<sub>2</sub>O<sub>6</sub>

This research deals with the synthesis and various characterizations of a couple of substituted columbite of MgNb2O6 and CaNb2O6 as well as making the solid solution of Mg1−xCaxNb2O6 (x = 0.00–1.00). Solid solutions are formed in the range of less than 4 % for Ca2+ substitution of MgNb2O6 (x < 0.04) and 8 % for Mg2+ substitution of CaNb2O6 (x ≥ 0.92). The preparation of Mg1−xCaxNb2O6 (x = 0.0–1.0) with atomic ratio Mg/Ca/Nb = 1.00 − x/x/2.00 was carried out by solid-state reaction. The synthesized compounds were well-characterized by X-ray diffraction (XRD) for revealing the structure, scanning electron microscopy (SEM) for analyzing surface morphology as well as chemical composition, and UV–Vis DRS (diffused reflectance spectroscopy) to estimate band gaps. XRD analysis shows that the structure of the crystals corresponds to an orthorhombic system of space group Pbcn(60). Electronics properties (band structure and density of state) were also calculated. Moreover, photoluminescence properties and photocatalytic activity were also measured under visible and ultraviolet light irradiation (showed photocatalytic activity).