A series of trichlorogermanate(II) salts (AGeCl 3 , A = Rb, Cs, CH 3 N H 3 , and (CH 3 ) 4 N) have been synthesized and characterized by 35 Cl NQR , 35 Cl NMR , AC conductivity, DTA, and X-ray diffraction techniques. In the temperature range studied two, two, five, and four phases were confirmed for the Rb, Cs, CH 3 NH 3 , and (CH 3 ) 4 N salts, respectively. From the 35 Cl NQR and structural data, isolated pyramidal GeCl 3 anions were recognized in the low temperature phases. With increasing temperature the relaxation times of the 35 Cl NQR decreased exponentially and the signals disappeared far below the melting point. This suggests that the reorientation of the anion about the pseudo three-fold axis is excited. With further increase in temperature, the ionic conductivity of CH 3 NH 3 GeCl 3 and (CH 3 ) 4 NGeCl 3 increased drastically at the phase transitions to their cubic perovskite phases (CH 3 NH 3 GeCl 3 :σ= 10 -1 Sm -1 at 400 K, (CH 3 ) 4 NGeCl 3 : σ = 5 x 10 -2 Sm -1 at 420 K). The mobile ion was confirmed to be the chloride ion by means of 35 Cl NMR and X-ray diffraction.
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Yamada et al. (1994) studied this question.