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Structure of crystalline and amorphous materials in the NASICON system Na1+xAlxGe2-x(PO4)3.
GAMMOND, Lawrence V. D.; AUER, Henry; SILVA, Rita Mendes da; ZEIDLER, Anita; ORTIZ-MOSQUERA, Jairo F.; NIETO-MUÑOZ, Adriana M.; RODRIGUES, Ana Candida M.; SILVA, Igor d'Anciães Almeida; ECKERT, Hellmut; BENMORE, Chris J.; SALMON, Philip S.
Abstract: The structure of crystalline and amorphous materials in the sodium (Na) super-ionic conductor system Na1+xAlxGe2-x(PO4)3 with x = 0, 0.4, and 0.8 was investigated by combining (i) neutron and x-ray powder diffraction and pair-distribution function analysis with (ii) 27Al and 31P magic angle spinning (MAS) and 31P/23Na double-resonance nuclear magnetic resonance (NMR) spectroscopy. A Rietveld analysis of the powder diffraction patterns shows that the x = 0 and x = 0.4 compositions crystallize into space group-type R ¯ 3 , whereas the x = 0.8 composition crystallizes into space group-type R ¯ 3 c. For the as-prepared glass, the pair-distribution functions and 27Al MAS NMR spectra show the formation of sub-octahedral Ge and Al centered units, which leads to the creation of non-bridging oxygen (NBO) atoms. The influence of these atoms on the ion mobility is discussed. When the as-prepared glass is relaxed by thermal annealing, there is an increase in the Ge and Al coordination numbers that leads to a decrease in the fraction of NBO atoms. A model is proposed for the x = 0 glass in which super-structural units containing octahedral Ge(6) and tetrahedral P(3) motifs are embedded in a matrix of tetrahedral Ge(4) units, where superscripts denote the number of bridging oxygen atoms. The super-structural units can grow in size by a reaction in which NBO atoms on the P(3) motifs are used to convert Ge(4) to Ge(6) units. The resultant P(4) motifs thereby provide the nucleation sites for crystal growth via a homogeneous nucleation mechanism.
Journal of Chemical Physics
v. 155, n. 7, p. 074501-1-074501-23 + supplementary material - Ano: 2021
Fator de Impacto: 3,488
    @article={003038878,author = {GAMMOND, Lawrence V. D.; AUER, Henry; SILVA, Rita Mendes da; ZEIDLER, Anita; ORTIZ-MOSQUERA, Jairo F.; NIETO-MUÑOZ, Adriana M.; RODRIGUES, Ana Candida M.; SILVA, Igor d'Anciães Almeida; ECKERT, Hellmut; BENMORE, Chris J.; SALMON, Philip S.},title={Structure of crystalline and amorphous materials in the NASICON system Na1+xAlxGe2-x(PO4)3},journal={Journal of Chemical Physics},note={v. 155, n. 7, p. 074501-1-074501-23 + supplementary material },year={2021}}