The double sulfate family (ABSO₄), where A and B are alkali metal cations, is the object of great interest owing to the complexity and richness of its sequence of phase transition induced by temperature variation. A new sulfate salt characterized by the presence of water molecule in the unit cell with the chemical formula, Li₂Na₃(SO₄)₂.6H₂O (LSSW), was obtained. The ultrasonic velocity measurement was done with pulse echo overlap technique [PEO]. All the six second order elastic stiffness constants, 𝐶₁₁ = 𝐶₂₂, 𝐶₃₃, 𝐶₄₄ = 𝐶₅₅, 𝐶₁₂, 𝐶₁₄ and 𝐶₁₃ = 𝐶₂₃ are reported for the first time. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the polar plots of phase velocity, slowness, Young’s modulus and linear compressibility in 𝑎–𝑏 and 𝑎–𝑐 planes.

The double sulfate family of (ABSO₄) where A and B are alkali metal cations, is the object of great interest owing to the complexity and richness of its sequence of phase transition induced by temperature variation. A new sulfate salt characterized by the presence of water molecule in the unit cell with the chemical formula, Li₂Na₃(SO₄)₂.6H₂O (LSSW), was obtained. The ultrasonic velocity measurement was done with pulse echo overlap technique [PEO]. All the six second order elastic stiffness constants, 𝐶₁₁ = 𝐶₂₂, 𝐶₃₃, 𝐶₄₄ = 𝐶₅₅, 𝐶₁₂, 𝐶₁₄ and 𝐶₁₃ = 𝐶₂₃, are reported for the first time. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the surface plots of phase velocity, slowness, Young’s modulus and linear compressibility in 𝑎–𝑏 and 𝑎–𝑐 planes.

The ultrasonic pulse echo overlap technique (PEO) has been used to measure the velocities of 10 MHz acoustic waves in sulphamic acid single crystals in the range of 300–400 K. This study evaluated all the elastic stiffnessconstants, compliance constants and Poisson’s ratios of the crystal. The temperature variations of the elastic constants have been determined. The phase transition studies above room temperature were investigated using ultrasonic PEO technique. This study has suggested new weak elastic anomalies for the crystal around 330 K. The transverse elastic constants C44 and C66 have shown clear thermal hysteresis of 2 K. The present differential scanningcalorimetric (DSC) studies carried out at a slow heating rate have also suggested weak phase transition around 331 K. The present elastic and thermal studies have been substantiated by already reported DC electrical conductivitystudies around 330 K.