Electrical and mechanical studies on ferroelectric lithium rubidium sulphate crystals

Slow evaporation method was used to grow single crystals of lithium rubidium sulphate with high transparency.Single crystal X-ray diffraction analysis shows that at room temperature,the crystal belongs to a monoclinic system with the space group P21/n.Some physical parameters like plasma energy,Penn gap,Fermi energy and electronic polarizability have been evaluated for the grown crystal.The relation between electronic polarizability and diamagnetic susceptibility for the crystal has been established on the basis of Kirkwood’s semiempirical equation.The ac conductivity and dielectric behavior of the grown crystal were systemically investigated as a function of frequency and temperature.The title compound obeys Jonscher’s power law relations:
ð(ω)=σo+Aω^(s),with exponent s<1.From the conduction study,it is observed that both small and large polarons take part in conduction process,and at low temperature,both the band and hopping mechanisms are responsible for conduction.From impedance and modulus studies,it is observed that only one conduction relaxation is observed in the crystal at low frequency.The activation energy of the dielectric relaxation(0.41 eV)and that of the conduction(Econd¼0:43 eV)are in agreement,as a result,there is no difference among the conduction and relaxation species at high temperature.Differential scanning calorimetric analysis of the crystal shows three endothermic peaks at 166℃,185℃,and 202℃,from which various thermodynamic parameters such asΔH,ΔS andΔC_(p) have been calculated.From Vickers hardness test,we have determined the mechanical strength,and other parameters which include fracture toughness,brittleness index,yield strength,and stiffness constant for the crystal.