The densities of mixed glass former 0.35 Na2O+0.65 [xB2O3+(1−x)P2O5] glasses related to the atomic fractions and volumes of short range structures

Christensen, Randilynn; Byer, Jennifer; Olson, Garrett; Martin, Steve W.

doi:10.1016/j.jnoncrysol.2011.10.018

Cited by 24 publications

(41 citation statements)

References 23 publications

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“…From the geometry of the trigonal bipyramidal structure and the estimated radii of sodium and oxygen, we determined that the largest exit point was in the x−y plane, between two oxygens, with a calculated doorway radius of r D = 0.71 Å. The volumetrically and compositionally dependent jump distance were calculated for the glasses in this study by using the molar volume (see previous study 32 ), r cation = λ Na = 2*(((3V M )/(4π))*(N Na / N glass )*(1/N A )) 1/3 , see Figure 11, where V M is the molar volume of the glass, N Na is the number of Na ions in one formula unit of the glass, N glass is the total number of ions in one formula unit, and N A is Avogadro's number. The high-frequency dielectric constant, ε, describes the high-frequency (short time scale) polarizability of the glass structure and decreases the Coulomb binding energy between cations and anions in the glass by reducing the effective electrical field strength between them.…”

Section: Calculation Of Parametersmentioning

confidence: 99%

Ionic Conductivity of Mixed Glass Former 0.35Na₂O + 0.65[xB₂O₃ + (1 – x)P₂O₅] Glasses

2013

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The mixed glass former effect (MGFE) is defined as a nonlinear and nonadditive change in the ionic conductivity with changing glass former fraction at constant modifier composition between two binary glass forming compositions. In this study, mixed glass former (MGF) sodium borophosphate glasses, 0.35Na 2 O + 0.65[xB 2 O 3 + (1 -x)P 2 O 5 ], 0 ≤ x ≤ 1, have been prepared, and their sodium ionic conductivity has been studied. The ionic conductivity exhibits a strong, positive MGFE that is caused by a corresponding strongly negative nonlinear, nonadditive change in the conductivity activation energy with changing glass former content, x. We describe a successful model of the MGFE in the conductivity activation energy terms of the underlying short-range order (SRO) phosphate and borate glass former structures present in these glasses. To do this, we have developed a modified Anderson-Stuart (A-S) model to explain the decrease in the activation energy in terms of the atomic level composition dependence (x) of the borate and phosphate SRO structural groups, the Na + ion concentration, and the Na + mobility. In our revision of the A-S model, we carefully improve the treatment of the cation jump distance and incorporate an effective Madelung constant to account for many body coulomb potential effects. Using our model, we are able to accurately reproduce the composition dependence of the activation energy with a single adjustable parameter, the effective Madelung constant, that changes systematically with composition, x, and varies by no more than 10% from values typical of oxide ceramics. Our model suggests that the decreasing columbic binding energies that govern the concentration of the mobile cations are sufficiently strong in these glasses to overcome the increasing volumetric strain energies (mobility) caused by strongly increasing glass-transition temperatures combined with strongly decreasing molar volumes of these glasses. The dependence of the columbic binding energy term on the relative high-frequency dielectric permittivity suggests that the increased polarizability of the bridging oxygens connecting SRO tetrahedral boron units to phosphorus units causes further charge delocalization away from the negatively charged tetrahedral boron units, leading to a lowering of the charge density, and is the underlying cause of the MGFE. Disciplines Materials Science and Engineering CommentsReprinted with permission from Journal of Physical Chemistry B 117 (2013) , 0 ≤ x ≤ 1, have been prepared, and their sodium ionic conductivity has been studied. The ionic conductivity exhibits a strong, positive MGFE that is caused by a corresponding strongly negative nonlinear, nonadditive change in the conductivity activation energy with changing glass former content, x. We describe a successful model of the MGFE in the conductivity activation energy terms of the underlying short-range order (SRO) phosphate and borate glass former structures present in these glasses. To do this, we have developed a modified Anderson-Stuart (...

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Section: Calculation Of Parametersmentioning

confidence: 99%

Ionic Conductivity of Mixed Glass Former 0.35Na₂O + 0.65[xB₂O₃ + (1 – x)P₂O₅] Glasses

2013

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“…To overcome these limitations, various materials with different chemical compositions were studied and published in the literature. Among these, the borate and borophosphate glasses have received a special attention.…”

Section: Introductionmentioning

confidence: 99%

“…To the best of our knowledge, only a few publications are reported regarding the structure and bioactivity of the calcium‐free B 2 O 3 − Na 2 O − P 2 O 5 system containing high concentrations of both network formers. Carta et al .…”

Section: Introductionmentioning

confidence: 99%

“…They characterized the structure of these glasses by using a combination of experimental techniques but without further testing their bioactivity. Additionally, Christensen et al . have recently published two works related to the physical properties of the 0.35Na 2 O + 0.65[ x B 2 O 3 + (1 − x )P 2 O 5 ] glasses, and they tried to explain the mixed glass former effect.…”

Section: Introductionmentioning

confidence: 99%

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The study of the structure and bioactivity of the B₂O₃ • Na₂O • P₂O₅ system

Hidi

Melinte

Ştefan

et al. 2013

J Raman Spectroscopy

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In this study, we have investigated calcium and silicate‐free samples over a wide compositional range in the xB2O3·30 Na2O·(70−x)P2O5 system, with 0 ≤ x ≤ 70 mol%, in order to determine the influence of the chemical composition on their structure and bioactive response in simulated body fluid. Information related to the chemical structures present in the network was obtained by means of Raman and infrared spectroscopy. For samples containing small amounts of P2O5, boron structures are preponderant. Upon increasing the phosphorus content, the samples' network is based on phosphate chains linked by boron groups through ‘P–O–B’ bridges. For high concentration of P2O5, the Q3 units form three‐dimensional network, whereas Q2 units assist the chain formation. Regarding the in vitro assessment of bioactivity, the clear print of PO4 asymmetric bending vibrations of apatite‐like layer in the 540–680 cm−1 spectral domain, the scanning electron micrographs and energy dispersive x‐ray analysis spectra demonstrate that the studied borophosphate samples exhibit good bioactive response only for certain chemical compositions. More exactly, the highest bioactivity is obtained for 30% and 20% B2O3 (mol%) after 3 and 11 days of immersion, respectively. Therefore, the samples with 20–30 mol% boron content are valuable candidates that can be used as materials for tissue engineering applications. Copyright © 2013 John Wiley & Sons, Ltd.

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“…19 It is reasonable to assume that a similar correlation exists here between bS and the T g s in the MGF ternary sulfide glasses under study here. The amount of bS can be calculated using the SRO atomic fraction model described in ref 18 and eq 6…”

Section: −34mentioning

confidence: 99%

Short Range Structural Models of the Glass Transition Temperatures and Densities of 0.5Na₂S + 0.5[xGeS₂ + (1 – x)PS_5/2] Mixed Glass Former Glasses

2014

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The 0.5Na 2 S + 0.5[xGeS 2 + (1 -x)PS 5/2 ] mixed glass former (MGF) glass system exhibits a nonlinear and nonadditive negative change in the Na + ion conductivity as one glass former, PS 5/2 , is exchanged for the other, GeS 2 . This behavior, known as the mixed glass former effect (MGFE), is also manifest in a negative deviation from the linear interpolation of the glass transition temperatures (T g ) of the binary end-member glasses, x = 0 and x = 1. Interestingly, the composition dependence of the densities of these ternary MGF glasses reveals a slightly positive MGFE deviation from a linear interpolation of the densities of the binary end-member glasses, x = 0 and x = 1. From our previous studies of the structures of these glasses using IR, Raman, and NMR spectroscopies, we find that a disproportionation reaction occurs between PS 7/2 4-and GeS 3 2-units into PS 4 3-and GeS 5/2 1-units. This disproportionation combined with the formation of Ge 4 S 10 4-anions from GeS 5/2 1-groups leads to the negative MGFE in T g . A best-fit model of the T g s of these glasses was developed to quantify the amount of GeS 5/2 1-units that form Ge 4 S 10 4-molecular anions in the ternary glasses (∼5-10%). This refined structural model was used to develop a short-range structural model of the molar volumes, which shows that the slight densification of the ternary glasses is due to the improved packing efficiency of the germanium sulfide species. Disciplines Materials Science and Engineering CommentsReprinted with permission ABSTRACT: The 0.5Na 2 S + 0.5[xGeS 2 + (1 − x)PS 5/2 ] mixed glass former (MGF) glass system exhibits a nonlinear and nonadditive negative change in the Na + ion conductivity as one glass former, PS 5/2 , is exchanged for the other, GeS 2 . This behavior, known as the mixed glass former effect (MGFE), is also manifest in a negative deviation from the linear interpolation of the glass transition temperatures (T g ) of the binary end-member glasses, x = 0 and x = 1. Interestingly, the composition dependence of the densities of these ternary MGF glasses reveals a slightly positive MGFE deviation from a linear interpolation of the densities of the binary end-member glasses, x = 0 and x = 1. From our previous studies of the structures of these glasses using IR, Raman, and NMR spectroscopies, we find that a disproportionation reaction occurs between PS 7/2 4-and GeS 3 2-units into PS 4 3-and GeS 5/2 1-

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The densities of mixed glass former 0.35 Na2O+0.65 [xB2O3+(1−x)P2O5] glasses related to the atomic fractions and volumes of short range structures

Cited by 24 publications

References 23 publications

Ionic Conductivity of Mixed Glass Former 0.35Na₂O + 0.65[xB₂O₃ + (1 – x)P₂O₅] Glasses

Ionic Conductivity of Mixed Glass Former 0.35Na₂O + 0.65[xB₂O₃ + (1 – x)P₂O₅] Glasses

The study of the structure and bioactivity of the B₂O₃ • Na₂O • P₂O₅ system

Short Range Structural Models of the Glass Transition Temperatures and Densities of 0.5Na₂S + 0.5[xGeS₂ + (1 – x)PS_5/2] Mixed Glass Former Glasses

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The densities of mixed glass former 0.35 Na2O+0.65 [xB2O3+(1−x)P2O5] glasses related to the atomic fractions and volumes of short range structures

Cited by 24 publications

References 23 publications

Ionic Conductivity of Mixed Glass Former 0.35Na2O + 0.65[xB2O3 + (1 – x)P2O5] Glasses

Ionic Conductivity of Mixed Glass Former 0.35Na2O + 0.65[xB2O3 + (1 – x)P2O5] Glasses

The study of the structure and bioactivity of the B2O3 • Na2O • P2O5 system

Short Range Structural Models of the Glass Transition Temperatures and Densities of 0.5Na2S + 0.5[xGeS2 + (1 – x)PS5/2] Mixed Glass Former Glasses

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Ionic Conductivity of Mixed Glass Former 0.35Na₂O + 0.65[xB₂O₃ + (1 – x)P₂O₅] Glasses

Ionic Conductivity of Mixed Glass Former 0.35Na₂O + 0.65[xB₂O₃ + (1 – x)P₂O₅] Glasses

The study of the structure and bioactivity of the B₂O₃ • Na₂O • P₂O₅ system

Short Range Structural Models of the Glass Transition Temperatures and Densities of 0.5Na₂S + 0.5[xGeS₂ + (1 – x)PS_5/2] Mixed Glass Former Glasses