Perovskite material, a kind of Functional Material was first found in the Ural Mountains and named after Lev Perovski who was the founder of the Russian Geographical Society. A perovskite structure has the generic form ABX3 and the same crystallographic structure as perovskite (the mineral). Perovskites, especially the doped ones, play a vital role in the modern field of materials science thanks to their interplay of structural, magnetic, and transport properties, superconductivity, colossal magnetoresistance, Jahn Teller effect, Phase transition, ferroelectricity etc. Their versatile applications include sensor materials, magnetic memory materials, ion conductors in fuel cells/sensors, Catalytic materials, photovoltaic etc. It is essential to have a thorough knowledge of their behaviour under various conditions to make the best utilization of such materials. In this book, based on the research work of the authors, the characterisation of lanthanum perovskite doped with monovalent sodium element carried out using the effective non-destructive ultrasonic studies has been discussed.