B. Jagadeesh et al., ORDER-DISORDER PHASE-TRANSITION AND DIMETHYL AMMONIUM GROUP-DYNAMICS IN [(CH3)2NH2]3SB2CL9- PROTON NMR-STUDY, Solid state communications, 91(10), 1994, pp. 843-847
Cation dynamics in tris(dimethylammonium) nonachloro-diantimonate, whi
ch exhibits paraelectric-ferroelectric phase transition, is studied th
rough proton spin lattice relaxation and second moment studies. Result
s show a clear signature of this phase transition. Analysis of the dat
a based on a recent model indicates a freezing of isotropic motion of
the dimethylammoiun (DMA) cation at the phase transition, as well as t
he existence of dynamically inequivalent DMA and methyl groups, both i
n the ratio of 1:1 in the low temperature phase. Activation energies a
ssociated with the dynamics of different inequivalent cations and meth
yl groups are calculated. These results are compared with similar stud
ies on related compounds comprising of tetramethyl and trimethyl ammon
ium groups.