High-temperature phase transitions ofLiRbSO4studied by magic angle spinning and multiple quantum magic angle spinning NMR of87Rb

Abstract

Solid-state nuclear magnetic resonance (NMR) of the {sup 87}Rb has been employed to investigate the phase transitions in polycrystalline LiRbSO{sub 4}. The spin-lattice relaxation time T{sub 1} and the NMR line shape were measured using magic angle spinning (MAS) and multiple quantum magic angle spinning (MQMAS) methods between 373 and 488 K. The quadrupole coupling constant, Q{sub cc}, the asymmetry parameter, {eta}{sub Q}, and the isotropic chemical shift, {delta}{sub CS}, were determined from the analysis of MAS and MQMAS spectra. The anomalies of Q{sub cc} near the IV-III phase transition were associated with the deformation of the local environment of the Rb ions in the crystal lattice. The measurements of the spin-lattice relaxation rate as a function of temperature and Larmor frequency showed the existence of a damped soft mode near the V-IV and IV-III phase transitions.