Structure of Na2O–GeO2–P2O5 glasses by X-ray and neutron diffraction

Hoppe, Uwe; Wyckoff, N.P.; Brow, Richard K.; Zimmermann, M. v.; Hannon, Alex C.

doi:10.1016/j.jnoncrysol.2014.02.013

Cited by 15 publications

(11 citation statements)

References 48 publications

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“…[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] The main bulk of these studies has been on alkali borophosphate glasses, [18][19][20][21][22][23][24][25][26][27][28][29] and also some work on germanophosphate glasses. [30][31][32][33][34][35] Additionally, there has been some efforts in extracting relevant length scales (see Appendix A) by analyzing the ionic conductivity and dielectric permittivity spectra in alkali ion based MGF systems. 17,[36][37][38] The main findings on changes in structural units and bonds as a function of relative composition of glass formers in borophosphate glasses containing Li2O or Na2O as network modifiers is that hetero-atomic bonds such as P-O-B are preferred to homo-atomic bonds such as P-O-P and B-O-B, for up to about 30 mol% borate content.…”

Section: Introductionmentioning

confidence: 99%

Insights from Local Network Structures and Localized Diffusion on the Ease of Lithium Ion Transport in Two Mixed Glass-Former Systems

et al. 2017

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The conductivity enhancement observed in the two glass systems, A: 40Li2O-(60-x)P2O5-xGeO2 and B: 40Li2O-10B2O3-(50-x)P2O5-xGeO2, as germanate content is increased from 0 to 25 mol% confirms the positive mixed glass-former effect (MGFE) in these systems. In this study, we further employ state-of-art NMR techniques along with Raman spectra to probe the local network structures. We use the MIGRATION concept to model the experimental conductivity and permittivity spectra obtained from impedance spectroscopy to understand scaling features of spectra and to calculate the value of the spatial extent of the localized diffusion of the lithium ion. As x increases from 0 to 25 mol%, for system A, a continuous increase of the POGe cross linkages as well as a continuous and strong modification of the phosphate network is observed. In system B, deeper analysis of the 31 P MAS-NMR experiments done using 2D 11 B/ 11 B homo-nuclear and 11 B/ 31 P hetero-nuclear NMR is used to determine the nature of the BOB linkages as well as that of POB linkages. Modelling of the conductivity spectra shows that the shape parameter of the spectra remains the same for both systems and for all compositions, a feature typical for MGFE. Further, correlating the trends of the spatial extent of localized diffusion with that gleamed from the local structures, we infer that as relative germanate content increases, in the ternary glass (system A) the ease of mobility of the Li + ion is enhanced while in the quaternary glass (system B, x > 0) it is somewhat hindered. Recently, using high-energy X-Ray photons in diffraction (HEXRD) on a synchrotron and neutron diffraction on a spallation source, Hoppe et al. 34 have detected six coordinated Ge in the structure of Na2O-GeO2-P2O5 glasses with high P2O5 contents and up to 24 mol% GeO2 fraction. Using thermal analysis, Raman, 31 P-MAS NMR and 23 Na NMR spectroscopy in the system (M2O)0.33[(Ge2O4)x(P2O5)1-x]0.67 (M = Na, K) Behrends & Eckert 35 infer that at low Ge2O4 contents (x = 0.2), the structure is dominated by pyrophosphate chains and unmodified Ge-O-Ge bonded four-membered ring units. At higher germanate contents hetero-atomic P-O-Ge linkages dominate. In general, it is found that the phosphate network is modified by the alkali ion preferentially, resulting in partially clustered cation distributions. The authors conclude that their study provides only an indirect confirmation of the germanate anomaly.

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Section: Introductionmentioning

confidence: 99%

Insights from Local Network Structures and Localized Diffusion on the Ease of Lithium Ion Transport in Two Mixed Glass-Former Systems

et al. 2017

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“…The decrease in the Ge coordination number upon nitridation might be explained on the basis of charge modifications within the glass system. When GeO 6 group forms, 2 neighboring PO 4 tetrahedra provide the GeO 6 unit with 2 additional electrons . Therefore, the P 5+ ions connected to GeO 6 possess a higher positive charge compared with those in pure phosphate environment, as part of the negative charge that was formally transferred to the GeO 6 .…”

Section: Resultsmentioning

confidence: 99%

“…This nonlinearity has indeed been suggested to be due to formation of sixfold coordinated GeO 6 units, detected in binary GeO 2 –M 2 O glass systems but also in ternary systems M 2 O–P 2 O 5 –GeO 2 glasses . Compositions with low M 2 O/GeO 2 or high Ge/P ratios have been found to favor GeO 6 formation, while other studies indicate that GeO 5 or GeO 6 formation, even at low germanium contents . The structure of germanophosphate glasses with low Ge/P ratios is considered to consist of heteroatomic P–O–Ge linkages that are favored over homoatomic P–O–P and Ge–O–Ge linkages …”

Section: Introductionmentioning

confidence: 99%

Structural impact of nitrogen incorporation on properties of alkali germanophosphate glasses

et al. 2018

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The structure, atomic packing density, calorimetric glass transition, and hardness of mixed sodium–lithium germanophosphate oxynitride glasses with varying Ge/P and N/P ratios were investigated. The combined influences of nitridation and mixed network former effect (MNFE) on the glass structure were analyzed using Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and 31P nuclear magnetic resonance (NMR) spectroscopy. Evidence for the existence of germanium in a higher coordination state, i.e., five‐ or sixfold coordination, was obtained by performing XPS analysis of the oxide glasses, with indication of conversion to tetrahedral coordination upon nitridation. Raman spectroscopy measurements implied that the germanate network was modified upon nitridation, including the removal of ring‐like germanate structures and P–O–Ge mixed linkages. The partial anionic N‐for‐O substitution gave rise to the linear dependence of the glass transition temperature (Tg) and hardness (HV) on nitrogen content (expressed as N/P ratio), especially for lower Ge/P ratio. However, nitridation also caused an unexpected increase in liquid fragility and decrease in density. This suggests that the governing structural parameter for property evolution in such LiNaGePON glasses is not only the increased degree of cross‐linking of the phosphate chains, but rather the short‐ and intermediate‐range structural modifications within the germanate component of the oxynitride glasses.

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“…For all the glassy materials, the S(k) functions display a shoulder at k 1 ∼0.85 Å−1 that is indicative of ordering on a real-space length scale of 2π/k 1 ∼7.4 Å. In Na 2 O-GeO 2 -P 2 O 5 glasses, the appearance of a similar feature has been linked to an inhomogeneous distribution of Na and Ge atoms [48].…”

Section: Pair-distribution Functionsmentioning

confidence: 91%

Structure of crystalline and amorphous materials in the NASICON system Na1+xAlxGe2−x(PO4)3

Gammond

Auer

Silva

et al. 2021

The Journal of Chemical Physics

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The structure of crystalline and amorphous materials in the sodium (Na) super-ionic conductor (NASICON) 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) 27 Al and 31 P magic angle spinning (MAS) and 31 P/ 23 Na 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 3c. For the as-prepared glass, the pair-distribution functions and 27 Al 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.

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Structure of Na2O–GeO2–P2O5 glasses by X-ray and neutron diffraction

Cited by 15 publications

References 48 publications

Insights from Local Network Structures and Localized Diffusion on the Ease of Lithium Ion Transport in Two Mixed Glass-Former Systems

Insights from Local Network Structures and Localized Diffusion on the Ease of Lithium Ion Transport in Two Mixed Glass-Former Systems

Structural impact of nitrogen incorporation on properties of alkali germanophosphate glasses

Structure of crystalline and amorphous materials in the NASICON system Na1+xAlxGe2−x(PO4)3

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