Phenomenon of high-temperature phase transition of RbH2PO4 crystals studied by 1H, 31P, and 87Rb NMR

The high-temperature phase transition phenomenon of RbH2PO4 single crystals were investigated by using a FT NMR spectrometer. The molecular dynamics of each ion in the high-temperature phase was studied by examining the relaxation times and the shifts of the resonance lines of the 1H, 31P, and 87Rb ions. The behavior that gives rise to the strong temperature dependence for spin-lattice relaxation time for 31P near 350 K (=TP) in RbH2PO4 is probably related to the re-orientational motion of the PO4 groups. As far as the surface and the spin-lattice relaxation time is concerned, the high temperature phenomenon exhibited near Td (=400 K) is not related to a physical change, but is instead related to a chemical change.

► High-temperature phase transition phenomenon of RbH2PO4.
► Shifts of the resonance lines and the spin-lattice relaxation times.
► Structural phase transition.
► Thermal decomposition.