Effect of alkali metal (Na, K) ion ratio on structural, optical and photoluminescence properties of K_0.5Na_0.5NbO₃ ceramics prepared by sol-gel technique

The method of preparation and its processing parameters have a strong effect on the structure and non-linear properties of the materials. A sol-gel technique is highly favoured owing to its lower production temperature, nanoparticle size, inter-diffusion of cations and cost-effectiveness. Sodium potassium niobate (KNN) is the most capable environmentally friendly material, which has been studied for the last decades as a promising candidate among all lead-free perovskites materials. In this article, we have prepared KNN ceramics by using the wet chemical sol–gel route. To control the volatility of (Na, K) ions at higher production temperature, we have added 10–20% (Na, K) alkali metal in the precursor solution. The phase investigation and crystalline character of the ceramics have been analysed by X-ray diffractometer. Raman spectroscopy analysis disclosed that pure KNN ceramic has a better crystalline and perovskite structure. FTIR analysis is done to analyse the presence of the functional group in the wavenumber range of 4000-500 cm^-1. The surface microstructure analysis and morphology of the KNN ceramics have been studied by using field emission scanning electron microscopy techniques. Further, the optical and photoluminescence behaviour has been studied at room temperature to know its practical applications in various electro-optic device applications. (author)