Structural changes in the compounds LiM{sub 2}{sup IV}(PO{sub 4}){sub 3} (M{sup IV}=Ge, Ti, Sn, and Hf) as followed by {sup 31}P and {sup 7}Li NMR
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (CSIC), 28049 Cantoblanco, Madrid (Spain)
From the {sup 31}P and {sup 7}Li NMR study of the compounds LiM{sub 2}(PO{sub 4}){sub 3} (M{sup IV}=Ge, Ti, Sn, and Hf), structural distortions of the NASICON (acronym for Na superionic conductors) network and the occupation of structural sites by lithium have been analyzed. In compounds with larger cations (M{sup IV}=Sn and Hf), structural distortions reduce the ideal symmetry of the NASICON framework (rhombohedral R{bar 3}c), producing the differentiation of three phosphorous sites. In these low-symmetry phases, PO{sub 4} tetrahedra distortions, deduced from the analysis of the {sup 31}P NMR chemical shift tensor, are higher than those of rhombohedral phases. These additional distortions are eliminated by sample heating above their corresponding transition temperature. On the other hand, from analysis of the dipole and quadrupole interactions of {sup 7}Li NMR spectra, recorded at low temperatures, it has been deduced that lithium atoms are located at M{sub 1} sites in the rhombohedral LiGe{sub 2}(PO{sub 4}){sub 3} and LiTi{sub 2}(PO{sub 4}){sub 3} and at M{sub 2} sites in the low-symmetry phases of LiSn{sub 2}(PO{sub 4}){sub 3} and LiHf{sub 2}(PO{sub 4}){sub 3} compounds. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 509041
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 55, Issue 21; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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