Ultrasonic Study of Elastic Anomalies in Lithium Sodium Sulphate Hexa Hydrate Single Crystal

The double sulphate family is of great interest these days. The crystal characterized with a space group C_3v⁶ with 6 molecules per unit cell belongs to trigonal symmetry with the lattice parameters a=b=8.451 Å and c=30.28 Å. The density of the material is measured to be 2.02×10³ kgm^-3. Large single crystals of Li₂Na₃(S0₄)₂.6H₂0 were Zrown by slow evaporation technique at a constant temperature of 308K. Phase transition studies based on the temperature variation of elastic constants of Lithium Sodium Sulphate Hexa hydrate single crystal, have been carried out using ultrasonic Pulse Echo Overlap technique. Temperature variation of the elastic constants C₁₁, C₃₃, C₄₄ and C₁₂ were measured from room temperature up to 330K. Results of the present investigation show that the elastic constant C₁₁ and C₃₃ undergo a weak elastic anomaly at around 316K. The other elastic constants do not show any anomalies.