The lithium isotope (⁶Li) effects in ALiSO₄ (A=NH₄, Rb)

Abstract

Lithium isotope (⁶Li) effects on crystal structures at room temperature and on phase transition points of NH₄LiSO₄ and RbLiSO₄ were investigated by X-ray diffraction and differential scanning calorimetry. The space group of NH₄ ⁶LiSO₄ was P2₁cn and that of Rb⁶LiSO⁴ was P2₁/n. It was found that thermal anomalies occur at 13, 153 and 186°C in NH₄ ⁶LiSO₄. The anomalous peak at 153°C does not correspond to the two phase transition points of NH₄LiSO₄ (10 and 186.5°C). In Rb⁶LiSO₄, we found a broad anomaly at around −40°C. It suggests that a possibility of a phase transition exists in a low temperature range.

Key Words:

• NH₄LiSO₄
• RbLiSO₄
• Isotope Effect
• Phase Transition
• X-ray Diffraction
• Differential Scanning Calorimetry