Nuclear magnetic resonance (NMR) studies of the local structure of phosphorus chalcogenide glasses: an overview

Mutolo, Paul F.; Witschas, Michael; Regelsky, Guido; Guenne, Joern Schmedt auf der; Eckert, Hellmut

doi:10.1016/s0022-3093(99)00520-7

Cited by 15 publications

(9 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Multinuclear ( 6 Li, 7 Li, 31 P) MAS NMR results show that the local environment found in the glassy state is unstable in the analogous crystalline form [15][16][17]. All crystalline P-S compounds reported here, exhibit a direct P-P bond of length around 2.30 Å .…”

Section: Introductionmentioning

confidence: 65%

Structural studies on xLi2S–(1−x)P2S5 glasses by X-ray diffraction and molecular dynamics simulation

Sistla¹,

Seshasayee²

2004

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 65%

Structural studies on xLi2S–(1−x)P2S5 glasses by X-ray diffraction and molecular dynamics simulation

Sistla¹,

Seshasayee²

2004

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

“…31 P NMR experiments yield populations of these units (Fig. 9) as a function of glass composition [56,57,66], and one finds the concentration of QT units to show a broad global maximum centered near x = 25%, while PYR units to show a maximum near x = 35%. ETY-like structures of r = 2.50 stoichiometry, as expected, show a maximum near x = 50% or r = 2.50.…”

Section: Binary Group V Selenidesmentioning

confidence: 99%

“…It translates to a connectivity that spans the 2.29 < r < 2.40 range, and is remarkably similar to the one in binary As x Se 1-x glasses. In binary P-Se glasses, evidence for three distinct Pcentered local structures is available from Raman scattering and 31 P NMR experiments [56,57,66] . These local structures include pyramidal (PYR) P(Se 1/2 ) 3 , quasi-tetrahedra (QT), Se=P(Se 1/2 ) 3 , polymeric ethylenelike (ETY)) P 2 Se 2 units [41,56] .…”

Section: Binary P-se Glassesmentioning

confidence: 99%

See 1 more Smart Citation

Intermediate Phases, structural variance and network demixing in chalcogenides: The unusual case of group V sulfides

Boolchand

Chen

Vempati

2009

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

Density functional theory Raman spectroscopy Medium-range order Short-range order Calorimetry Enthalpy relaxation Structural relaxation a b s t r a c tWe review intermediate phases (IPs) in chalcogenide glasses and provide a structural interpretation of these phases. In binary group IV selenides, IPs reside in the 2.40 < r < 2.54 range, and in binary group V selenides they shift to a lower r, in the 2.29 < r < 2.40 range. Here, r represents the mean coordination number of glasses. In ternary alloys containing equal proportions of group IV and V selenides, IPs are wider and encompass ranges of respective binary glasses. These data suggest that the local structural variance contributing to IP widths largely derives from four isostatic local structures of varying connectivity r, two include group V based quasi-tetrahedral (r = 2.29) and pyramidal (r = 2.40) units, and the other two are group IV based corner-sharing (r = 2.40) and edge-sharing (r = 2.67) tetrahedral units. Remarkably, binary group V (P, As) sulfides exhibit IPs that are shifted to even a lower r than their selenide counterparts; a result that we trace to excess S n chains either partially (As-S) or completely (P-S) demixing from network backbone, in contrast to excess Se n chains forming part of the backbone in corresponding selenide glasses. In ternary chalcogenides of Ge with the group V elements (As, P), IPs of the sulfides are similar to their selenide counterparts, suggesting that presence of Ge serves to reign in the excess S n chain fragments back in the backbone as in their selenide counterparts.Ó 2009 Elsevier B.V. All rights reserved. Three types of glass transitionsGlasses are intrinsically non-equilibrium solids and their physical properties generally evolve over long times, i.e., these solids slowly age. The aging of glasses is itself a fascinating subject and has been debated since the early work of Kohlrausch [1-3]. There is now evidence to suggest that the stretched exponential relaxation observed in glasses may well be characterized by specific exponents, which are determined [2] largely by the nature (of long or short range) of forces that control how traps or defects diffuse as networks relax. For a long time it was widely believed that glass transitions are also hysteretic and age [3] as observed in a traditional differential scanning calorimetry. There are new findings showing that under select conditions [4-6] aging of glasses may not occur.New insights into the nature of the glass transition [4,7] have now emerged using modulated-DSC (m-DSC). A significant advantage of m-DSC over traditional DSC is that the method permits deconvoluting the total heat flow into a reversing heat flow term (which captures the local equilibrium specific heat) and a nonreversing heat flow term (which captures non-equilibrium effects of the changing structure). The thermally reversing heat flow term usually reveals a rounded step-like jump. One defines the glass transition temperature, T g , from the inflexion point of the step, and the specific hea...

show abstract

“…In contrast to these network chalcogenide glasses, relatively little is known regarding the structural characteristics and structure-property systematics of chalcogenide glasses with modified networks. From a practical point of view, however, simply modified chalcogenide networks are not good glassformers due to their thermal instability against devitrification and low solubility of alkali and/or alkaline-earth sulfides and selenides in Ge-As-P-X networks [11][12][13][14][15] One way to improve the thermal stability and to incorporate significant amounts of alkali or alkaline-earth modifiers and rare earths in these glasses is to create a compensated network via addition of refractory trivalent cations that are glass-forming intermediates such as Ga 3+ [16][17][18]. In this case the modifier cations are expected to charge balance the [Ga(S/Se) 4 been extensively studied in the literature.…”

Section: Introductionmentioning

confidence: 99%

Structure and physical properties of glasses in the system Ag2Se–Ga2Se3–GeSe2

Marple

Kaseman

Hung

et al. 2016

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

Homogeneous glasses in the ternary system Ag 2 Se-Ga 2 Se 3-GeSe 2 are synthesized and their structure is characterized using Raman and one-and two-dimensional 77 Se, 71 Ga and 69 Ga nuclear magnetic resonance (NMR) spectroscopy. The structure of these glasses consists predominantly of a charge-compensated network of corner-sharing (Ga/Ge)Se 4/2 tetrahedra where the negatively charged GaSe 4/2 tetrahedra are charge balanced by the Ag cations. The deficiency in Se required to satisfy the tetrahedral coordination of Ga in glasses with Ag 2 Se:Ga 2 Se 3 < 1 is accommodated by the formation of homopolar Ge-Ge bonds. Progressive addition of Ag 2 Se to these glasses efficiently removes Ge-Ge bonding such that their concentration essentially goes to zero at the chemical threshold Ag 2 Se:Ga 2 Se 3 = 1. Further addition of Ag 2 Se beyond this threshold (i.e., Ag 2 Se:Ga 2 Se 3 > 1) results in the modification of the Ga,Ge-Se tetrahedral network via depolymerization and formation of non-bridging Se atoms. Moreover, all glasses irrespective of their Ag 2 Se:Ga 2 Se 3 ratio contain a small fraction of Se-Se bonds, implying violation of chemical order. Therefore, the compositional evolution of the structure of these glasses displays the characteristics of both the isoelectronic alkali/alkalineearth aluminosilicate glasses and the purely covalent, continuously alloyed chalcogenide networks. Such composition-dependent structural evolution is shown to be consistent with the corresponding variation in glass transition temperature and molar volume.

show abstract

Nuclear magnetic resonance (NMR) studies of the local structure of phosphorus chalcogenide glasses: an overview

Cited by 15 publications

References 33 publications

Structural studies on xLi2S–(1−x)P2S5 glasses by X-ray diffraction and molecular dynamics simulation

Structural studies on xLi2S–(1−x)P2S5 glasses by X-ray diffraction and molecular dynamics simulation

Intermediate Phases, structural variance and network demixing in chalcogenides: The unusual case of group V sulfides

Structure and physical properties of glasses in the system Ag2Se–Ga2Se3–GeSe2

Contact Info

Product

Resources

About