Structural, Optical, and Compactness Characteristics of Nanocrystalline Synthesized through an Autoigniting Combustion Method

Nanoparticles of calcium metaniobate compound are prepared by an autoigniting combustion technique and its structural, optical, and dielectric properties are investigated. The X-ray diffraction, Fourier-transform Raman, and infrared studies reveal that calcium metaniobate possesses phase pure orthorhombic columbite structure with space group of Pbcn. The average particle size of the as-prepared nanoparticles obtained from both the Scherrer formula and transmission electron microscopy is ~37？nm. The optical band gap calculated from Tauc's Plot is 3.25？eV. Photoluminescence studies reveal that Calcium metaniobate can be used as an idealphotoluminarmaterial. The powders are pelletised and sintered at an optimized temperature of in a short duration of two hours, yielding a high density. The morphology of the sintered pellet is further examined using scanning electron microscopy. The dielectric constant and loss factor values measured at 5？MHz for a well-sintered Calcium metaniobate pellet are found to be 27.6 and respectively, at room temperature. 1. Introduction Calcium metaniobate (CaNb2O6) crystallizes with orthorhombic columbite structure in the space group of Pbcn(60) and is a strong source of coherent light which can be useful in applications of holography [1]. CaNb2O6 crystal possesses a low-symmetry crystal structure and the Ca and Nb cations are at the centre of the octahedra surrounded by six oxygen atoms in the CaNb2O6 columbite structure. The CaO6 and NbO6 octahedra form independent zigzag chains by sharing edges and the chains are connected by sharing corners in the order of CaO6 chain-NbO6 chain-NbO6 chain [2, 3]. CaNb2O6 has good mechanical, dielectric, and thermal properties like thermal conductivity, specific heat, and thermal coefficient of expansion making it suitable for laser crystal host, substrates for electronic circuits, and so forth [1, 3]. The photocatalytic activity of CaNb2O6 is studied by a number of researchers and Cho et al. reported its enhanced photocatalytic activity for producing H2 from pure water under UV irradiation [4–7]. CaNb2O6 also exhibits strong blue luminescence emission under UV light irradiation at 300？K. CaNb2O6 also possesses interesting properties, namely, piezoelectricity, pyroelectricity, and electrooptic and nonlinear optical activity [8–11]. The compacted calciummetaniobate (CaNb2O6) is a good dielectric material for microwave dielectric applications [12–14]. CaNb2O6, a subcomponent of the complex perovskite family A( )O3 prepared by the conventional route, has been studied for its microwave dielectric