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Yrr. N. MOSKVICH et al.: NMR Study of Internal Motions in M,SbF, 615 phys. stat. sol. (b) 166, 615 (1989) Subject classification: 76.60; 66.30; 72.20; S9.16 L. V . Kirenskii Institute of Physics, Academy of Sciences of the USSR, Siberian Branch, Krasnoyarskl) ( a ) and Institute of Chemistry, Academy of Sciences of the USSR, Vladivostok (b) NMR Study of Internal Motions in a New Family of Ionic Conductors MzSbFs BY Yu. N. MOSKVICH (a), B. I. CHERKASOV (a), A. M. POLYAKOV (a), A. A. SUKHOVSKII (a), and R. L. DAVIDOVICH (b)lgF NMR spectra and relaxation times TI, T2, TI, and electric conductivity in isostructural polycrystalline pentafluoroantimonates (111) M,SbF, (M = Rb, K, Cs, Ti, NH,) are measured. It is found that the observed changes in the NMR spectra and relaxation times with temperature are determined by three types of motion : anisotropic and isotropic reorientations of [SbF,El2octahedra and diffusion motion of the fluorine ions. Parameters of these motions are found. All the compounds investigated show high conductivity a t high temperature, amounting in the case of thallium and ammonium salts the values of u = lo1 to loo Q-l m-l typical of superionic crystals.It is shown that the observed high conductivity is determined by fast diffusion motion of fluorine ions. On the basis of the data obtained a mechanism of fluorine ion diffusion is proposed. I n (NH,),SbF, at 398 K a phase transition is found. H3MepeHbI CIIeKTpbI HMP H BpeMeHa PeJIaHCaqHH I , , T,, TI, HHep "F H 3JIeRTpOIIpOBOn-HOCTb B H30CTpYKTYpHOM PRAY IIOJIMIiPMCTaJIJIH9eCEiHX lIeHTa@TOpOaHTMMOHaTOB (111) M,SbF,, M = K, Rb, CS, T1, NH,. yCTaHOBJIeH0, 9 T O ~a6~1mxam11piec~ H3MeHeHMH CneKTpOB RMP rUHPOKMX JIHHMg, BbICOKOrO pa3pelUeHHH I.I BpeMeH PeJIaKCaUHIi C TeM-IIepaTypOfi 06yCJIOB.i1eHb1 TpeMFl BHAaMH nBHweHHH: aHH30TPOIIHbIMH H H30TPOllHbIMH peopMeHTaqMRMM OKTa3ApOB [SbF,E]'-Ei aM@@Y3HOHHhIM HBMZeHHeM MOHOB @Topa. OIIpeHeJIeHbI IIapaMeTpbl 3THX ABHW€!HM@. B O BCeX HCCJIeAOBaHHblX COeHHHeHMRX I I P M BbICOKMX TeMllepaTypaX 06HapymeHa BblCOKaR IIpOBOAHMOCTb, nOCTHramll1aFl B CyIIepHOHHbIX HpHCTaJIJIOB. nOKa3aH0, 9 T O ~a 6~1 m~a e~a~ BblCOKaH IlPOBOALrMOCTb 06yCJIOBneHa 6bICTphIM AH@@Y3HOHHbIM aBM%eHMeM MOHOB @Topa. H a OCHORe lIOJIy-geHHbIX AaHHbIX npenJIomes MeXaHH3M aH@@Y3HH MOHOB #Topa. B (NH,),SbF, IIpM 398 K 06HapyHWH @a30BbIt nepexox. cnysae coneii T a m m H a M M o H m a~a s e~u B u = lo1 no i O o C..' m-l, xapaKTepHbrx HJIR

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A detailed study of the temperature and angular dependences of the 77Se and 2D NMR spectra in the ferroelectric phase of ammonium hydrogen selenate NH4HSeO is performed. It is found that in this phase the NMR lines corresponding to each of three structurally non‐equivalent selenium and deuterium nuclei in the triclinic unit cell are split into six components of equal intensities. It is established also that the doubling of the DMR line number is connected with the formation of ferroelectric domains in the AHSe. An additional triplication of the line number is due to the existence of superstructure in the ferroelectric phase of NH4HSeO4 cuused by the triplication of one of the unit cell parameters of the paraelectric phase structure.

High‐resolution 77Se NMR spectra in single crystals of cesium trihydrogenselenite are measured at 14.09 kG and different temperatures using the cross‐polarization method. The chemical shift tensors of all structurally non‐equivalent selenium nuclei are determined from the angular dependences of spectra separate lines in paraelectric and antiferroelectric phases. It is established that chemical shift tensor parameters are closely connected with SeO3 group geometry reflecting its distortion degree. The phase transition to the ordered phase is accompanied by increasing of SeO3 group distortion due to the ordering of protons on hydrogen bonds. The marked anisotropy of the 77Se NMR separate linewidths is founded. An analysis of the theoretical and experimental angular dependences of line second moments shows that the observed anomalous broadening is caused by indirect magnetic interaction between 77Se and 133Cs nuclei of the Cs+—HSeO3− fragment in crystals. The principal values of the indirect dipolar interaction tensor of this selenium nucleus are determined in the paraelectric phase.