In this paper, lead-free sodium potassium niobate thin films have been prepared by using a chemical solution deposition-based spin coating route. The effect of different anealing temperatures on structural and optical properties hasbeen studied. The phase analysis of thin films was investigated by using X-ray diffraction analysis. The microstructure and surface roughnes of thin films were studied by using atomic force microscopy. Raman spectroscopy analysis revealed that increase in annealing temperature gives rise to better crystallinity and perovskite phase. Optical parameter of thin films has been studied by using reflectance spectroscopy at room temperature. Photoluminescence analysis has been conducted by using an exciting wavelength of 300 nm at room temperature.

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 perovskitestructure. 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.

Non-toxic lead-free potassium sodium niobate (K$_{0.5}$Na$_{0.5}$NbO$_3$) ceramics were manufactured by using solidstate reaction method. The influences of excessive alkali metal (Na, K) ions concentration (0–20%) on their structural and electro-optical properties have been examined systematically. The structural properties confirmed the perovskite phase having orthorhombic crystal structure without any secondary phase even on the addition of excessive quantities of (Na, K) ions. Optical properties revealed decrease in optical bandgap energy with increase in the (Na, K) ions ratio. Photoluminescence spectrum shows the emission band in the UV–visible region, which makes KNN a suitable candidate for telecommunication devices, optical storage technology and LEDs. Impedance study revealed the negative temperature coefficient of resistance and non-Debye nature of the synthesized samples.