Mechanical, theoretical and dielectric studies on ferroelectric lithium ammonium sulphate (LAS) single crystals

Lithium ammonium sulphate (LAS) is an excellent inorganic ferroelectric material with a very high degree of transparency and exceptional mechanical properties. Good quality crystals of LAS were grown by using the modified Sankaranarayanan–Ramasamy method within a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Several solid state physical parameters have been determined for the grown crystals. The anisotropy in Vickers’ micro hardness led to the study of various parameters such as fracture toughness (Kc), brittleness index (B) and yield strength (σv). The dielectric constant and the dielectric loss of the grown crystal were studied as a function of frequency and temperature, and the corresponding relaxation time (τ), relaxation frequency (Fr) and the activation energy have been calculated.