MARTENSITIC PHASE-TRANSITIONS IN METHYLAMMONIUM HEXACHLOROTELLURATE (CH3NH3)2TECL6 AS STUDIED BY PULSED CL-35 NQR

The fraction transformed during the III-V and IV-III phase transitions in (CH3NH3)2TeCl6 was measured by use of the pulsed Cl-35 NQR method to study the martensitic nature of the transitions. The phase transiti ons could be suspended at any stage of the transition and the coexiste nce of two phases was observed in a fairly wide temperature range. For each of the two transitions, the onset of the transition was found to be depressed by the accumulation of lattice imperfections caused by t he repetition of the phase transitions or grinding. T2 was used to es timate the degree of lattice imperfection. The NQR method was shown to be a convenient method to study martensitic phase transitions.