抄録
The phase transitions of a ferroelastic CsPbCl3 single crystal grown by using the Bridgman method have been investigated using 133Cs and 207Pb nuclear magnetic resonance (NMR). Two sets of seven-line 133Cs NMR signals were obtained instead of a simple seven-line structure. From the experimental data, the 133Cs NMR parameters were obtained in the temperature range from phase I to phase IV. These showed the same magnitudes for the quadrupole coupling constants and the asymmetry parameters for the resonance lines of the two sets, but with different orientations. Near the transition temperatures 37°C and 47°C, the NMR parameter of the 133Cs nucleus changed abruptly, which means that first-order phase transitions occurred at 37°C and 47°C, whereas a second-order phase transition occurred at 42°C. In addition, the nuclear spin–lattice relaxation time of the Cs nucleus in this crystal revealed a discontinuity at 47°C while the Pb relaxation time seems to be continuous in the temperature. The abrupt change in the 133Cs relaxation time near 47°C is due to the critical showing down of the soft mode. Our relaxation time results indicate that the phase transitions might be attributed to the dominant relaxation mechanism.
