Structure Of Phosphate Glasses Research Articles

Effect of three-body interaction on structural features of phosphate glasses from molecular dynamics simulations.

Understanding the structures of phosphate glasses is important to many of their technological applications. Molecular dynamics simulations are commonly used to generate structure models of sodium phosphate glasses, and those with partial charge pairwise potentials have been successfully applied for modeling other network glasses, such as silicate and aluminosilicate glasses. In this work, we show that the addition of a three-body term is essential in regulating the intertetrahedral bond angles, as well as Qn speciation in comparison to experiments. Simulation results with and without three-body terms were compared and validated with experimental results, including neutron structure factors. Further comparison with glass structures fully relaxed with first-principles density functional theory was performed to evaluate the simulation results. The results show that the addition of three-body terms is vital for the modeling of phosphate glasses, and it can significantly improve the description of short- and medium-range structures and properties.

The influence of phosphate glass structure on results of thermal poling

Two sodium phosphate glasses with different structure (meta- and orthophosphate ones) were thermally poled well below the glass transition temperatures. Glass with an orthophosphate structure (glass LA30) demonstrated a typical behavior of polarization current, that is, monotonic current decrease; however, in glass with a metaphosphate structure (glass LA10) the current first increased for 15–20 min and only then started monotonic decreasing. In spite of the similar sodium content, the current in LA10 glass exceeded the one in LA30 glass by about 10 times. This is explained by the capability of substituting intrinsic sodium ions by more mobile protons entering LA10 glass with a metaphosphate structure from the atmosphere. The other difference consists in the fact that the subanodic layer of LA10 glass after poling has many small cracks, while the subanodic layer of LA30 glass is crystallized. It should be emphasized that the crystallization of phosphate glasses under dc electric field below glass transition temperature is observed for the first time. In addition, after poling, no changes in the refractivity of both glasses were detected, but the generation of the second optical harmonic in LA30 glass was observed.

The oxygen environments of divalent cations in phosphate glasses and crystals – the changes with composition and ionic radii

Besides the PO4-based networks, the structure of phosphate glasses is determined much by the modifier cations. The consideration is focused on glasses (MeO)x(P2O5)1-x with divalent modifiers with concentrations x = 0.33 and 0.50. The packing densities and Me−O coordination numbers of the glasses and the related crystals are compared. The MeP4O11 crystals and the glasses at x = 0.33 have MeO6 octahedra for all Me dimensions from Zn to Ca. At x = 0.50, the structures of crystals and glasses show a large variability with different Me−O coordination numbers of 4, 5, 6, and 7 for the Me = Zn, Mg, Fe, Co, Mn, Cd, and Ca. Several factors beyond the ionic radii influence the MeOm polyhedra. Heterogeneities of 1 nm dimension known from small-angle X-ray scattering experiments of the Mg(PO3)2 glass are explained by small clusters of interconnected MgO6 units within a matrix of isolated MgO5 pairs.

Deciphering the hierarchical structure of phosphate glasses using persistent homology with optimized input radii

Deciphering the hierarchical structure of phosphate glasses using persistent homology with optimized input radii

First investigation of the effect of strontium oxide on the structure of phosphate glasses using molecular dynamics simulations

Phosphate glasses have features that separate them from other materials such as borates, silicates, and tellurides, and they can be employed in a variety of applications including optics, electronics, medicine, and environmental protection. However, these pure phosphate glasses have low chemical durability, which limits their application. The addition of strontium to the glass considerably improves its durability. The effect of SrO addition in a glass phosphate structure with a formal chemical composition of (100 - x) P2O5 – x SrO (where x = 0, 5, 10, 15… 45 mol. %) was studied using classical molecular dynamics simulations. According to the progressive increase in the SrO content, the density of the simulated glass increased from 2.400 g/cm3 to 2.937 g/cm3, while its molar volume values reduced from 59.143 to 42.449 cm3/mol. The short-range structure of the simulated glasses is described and agrees well with prior experimental and theoretical research. The increased SrO level in the glass resulted in the depolymerization of the phosphate network, according to simulations. Furthermore, we evaluated the aggregation parameter of the Sr-Sr pair, and it was most intense because of the low SrO content, which can lead to the inhomogeneity of the phosphate glass network.

Influence of P<sub>2</sub>O<sub>5</sub> Content on In Vitro Behavior of CaO-ZnO-P<sub>2</sub>O<sub>5</sub> Bioglass Powder Compacts

CaO-ZnO-P2O5 bioglasses were synthesized in order to study the relationship between their composition and in vitro behavior. We specifically examined the relationship between the P2O5 content and the in vitro behavior of the powder compacts. The weight gain percentage after immersion in a simulated body fluid (SBF) for a 4-week-period increased with the increase in P2O5 content up to a certain threshold, and the maximum weight gain was observed when the P2O5 content was 33.6 mol%. As the amount of P2O5 increased further, the weight gain in the samples rapidly turned to a negative value. In other words, it was found that there was a threshold for the P2O5 content. In the sample that had the maximum weight gain, submicron level, round precipitates were observed after the SBF test and presumed to be an amorphous calcium-zinc phosphate substance. Furthermore, a phosphate glass structure that promotes the precipitation of the above substances was proposed. The structure was formed when the long-chain structure of P-O (Q2 group), which promotes the dissolution of the P component, and the short-chain structure of P-O (Q0 and Q1 groups), which are considered to be the starting points of precipitation, coexist in a well-balanced ratio within the glass.

A career in diffraction: probing the structure of phosphate glasses

A career in diffraction: probing the structure of phosphate glasses

Effect of Fe<sub>2</sub>O<sub>3 </sub>Contents on the Ions Release from Phosphate-Based Glass

Currently, phosphate-based glasses have been extensively studied for their special characteristic of being soluble in aqueous medium and capable of releasing ions. This paper presents the relationship between the solubility properties and ion released of phosphate glasses having a composition of 6Al2O3-15K2O-14Na2O-(20-x)CaO-xFe2O3-45P2O5, where x = 2, 4, 6 and 8 wt.%. Clear and free bubbles of dark green glasses were obtained from the used of conventional melting technique at 1300 oC. The ion released and weight loss studies were determined from the immersion of the glass samples in deionised water for about 16 weeks under static condition. IR spectra revealed the formation of phosphate units such as metaphosphate and orthophosphate unit around 1097 cm-1 and 1107 cm-1 with the presence of Fe2O3 in the glass system. SEM image of the phosphate glass structure before and after immersion seems to be associated with the solubility of these glasses. From the study, the concentration of Na+ and K+ release decreased when more Fe2O3 contents were added to the system. Fe2O3 stabilize the network structure via the formation of P-O-Fe bond which more hydration resistant towards water penetrating molecules.

Thio-oxynitride phosphate glass electrolytes prepared by mechanical milling

Abstract

Structure and electrical properties of a new thio-phosphorus oxynitride glass electrolyte

For the first time, a thio-phosphorus oxynitride glass containing nitrogen and sulfur, LiPOSN, has been prepared by a melting process in two steps and its manipulation is possible in air without any decomposition. The anionic substitution of oxygen by sulfur and nitrogen in the phosphate glass structure has been confirmed by 1D 31P solid state NMR and XPS. The 2D 31P DQ-SQ experiment indicates that S bearing phosphate groups are integrated into the global phosphate network and do not form clusters. Through the study of the properties of this glass, it was verified a decrease of the glass transition temperature, due to the depolymerization of the phosphate network when lithium sulfide is introduced into the oxynitride glass, along with a pronounced increase of the ionic conductivity, that suggest that this glass can be considered as a new highly conductive and corrosion resistant glass electrolyte.

Structural, optical and mechanical properties of ternary CaO-CaF2-P2O5 glasses

The ternary phosphate glass series (50−x)CaO-xCaF2-50P2O5 (x = 0–20 mol%) were synthesized using melt quench technique. Structural, optical and mechanical properties were investigated with increase in CaF2 content. Using X-ray diffraction (XRD), synthesized glasses were confirmed to be amorphous in nature. Replacement of oxygen ions by fluorine ions increased the values of density. Decrease in refractive index due to the low polarizability of fluorine ions in the glass matrix was observed. In Fourier transform infrared (FTIR) spectra, the slight variation in νas (PO2) band position and intensity could be attributed to replacement of fluorine ions for oxygen ions in phosphate glass structure. These data were well supported by Raman spectra. Optical band gap energy increased from 3.44 eV to 3.64 eV with increase in CaF2 content, and Urbach energy decreased suggesting that the fluorine ions reduced the tail energy states in the band gap compared to the oxygen ions. Mechanical parameters such as Vickers hardness, fracture toughness and brittleness were evaluated from the Vickers micro indentation measurements. Increase in Vickers hardness, decrease in fracture toughness and increase in brittleness were observed with increase in CaF2 content.

Synthesis of Optically Uniform Glasses Containing Gold Nanoparticles: Spectral and Nonlinear Optical Properties

A method for preparing batches, melting, producing and modifying the structure of phosphate glass on a nanoscale by introducing gold nanoparticles were developed. Samples of glass with different content of phosphorus oxide were synthesized. The samples were heat-treated in a gradient furnace. Their physical, spectral and nonlinear optical properties were studied.

Correlation between Protonic Conductivity and Structure of Phosphate Glasses for Intermediate Temperature Fuel Cells

We measured NMR, Raman spectra and AC impedance for BaO-ZnO-P2O5 glasses. The short-range order of these glasses was based on metaphosphate (Q P 2) structure. A part of O-P-O bonding was broken and the mobile proton concentration increased for ternary BaO-ZnO-P2O5 glasses. The protonic conductivity was 2 × 10-7 S/cm for 30 mol%ZnO-10 mol%BaO-60 mol%P2O5 glass at 200 oC. Co-doping of the cations with different coordinate numbers is effective to improve the protonic conductivity for phosphate glasses.

Investigations on In Vitro and Degradation Properties of ZnO‐Added Phosphate‐Based Glasses and Glass Ceramics

A series of phosphate based glasses of composition 45P2O5–(40−x)CaO–15Na2O–xZnO (x = 0, 3, 6, 8 10, and 12 mol%) were prepared employing melt‐quenching techniques. Based on the thermal analysis data of glasses, the schedule of thermal treatments have been designed and employed to obtain their glass ceramic derivatives. The increase in thermal stability and decrease in crystallization tendency was observed from differential thermal analysis traces. The durability of phosphate glasses were improved as a result of the addition of ZnO content. The increasing ZnO content alters the phosphate glass structure and enhances the cross‐link formation between different network chains. A broad‐based characterization approach combining different techniques was used to investigate the in vitro properties of glasses and their glass‐ceramic equivalents against the addition of ZnO content into the glass composition. The in vitro results revealed the decreasing nature of apatite forming ability of phosphate glasses with increase in ZnO content before and after thermal treatments. Both the glass and glass‐ceramics containing ZnO content above 10 mol% exhibited poor in vitro performance mainly because of their dissolution nature. The weight loss analysis revealed that the decreasing solubility of glass and glass‐ceramics was observed as increasing of ZnO content.

Correlation between Protonic Conductivity and Structure of Phosphate Glasses for Intermediate Temperature Fuel Cells

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Properties and Structure Investigation of Rare Earth-Doped Zinc Aluminum Silica-Phosphate Glasses

This study explores a series of optical, thermal, and structural properties based on zinc-aluminum phosphate glasses that doped with varied rare earth (RE) elements Yb2O3 and P2O5 components replaced by SiO2. It was found that for 60P glasses system, 7 mol% Yb2O3 doped has the maximum fluorescence but quenching when Yb2O3 is doped up to 9 mol%. In addition, with increasing the content of Yb2O3 the absorption intensity increased. According to Raman spectra, we found the Yb3+ and Si4+ ions for the impact of network structure of glass, SiO2 added to make the network structure of phosphate glasses at 450-500cm-1 and 600-650cm-1 were formed O-T-O bond and T-O-T bond(T=Si, Al).

Neutron scattering and ab initio molecular dynamics study of cross-linking in biomedicalphosphate glasses

Details of the microscopic structure of phosphate glasses destined for biomedicalapplications, which include sodium, magnesium and calcium cations, have beenobtained from the static structure factor measured by means of neutron scattering. Acomplementary, molecular dynamics study has been performed on a range ofphosphate glasses using density functional theory methods, which allow structuralfluctuations, including bond breaking, in the liquid phase before quenching to the glassphase. Good agreement between experiment and simulation allows the moleculardynamics trajectories to be analysed in detail. In particular, attention is focusedon the cross-linking of divalent cations in contrast with the structural aspectsassociated with monovalent cations. Magnesium cations are found equidistant andbridging between the phosphorus atoms of different phosphate chains, leading toa shorter phosphorus–phosphorus second neighbour distance (that is, a morecompact packing of neighbouring phosphate chains) compared to the effect ofsodium cations. Calcium cations show behaviour intermediate between those ofmagnesium and sodium. Molecular dynamics simulations give access to the cationmobility, which is lowest for magnesium, reflecting its structural, cross-linking role.

Effect of TiO 2 addition on structure, solubility and crystallisation of phosphate invert glasses for biomedical applications

Phosphate invert glasses in the system P 2O 5–CaO–MgO–Na 2O are completely soluble and exhibit a neutral pH in aqueous media, and they are therefore of interest for use as degradable implant materials. Their structure consists of small phosphate units such as pyrophosphate (P 2O 7 4 −), and hence they are prone to crystallisation. Addition of TiO 2 is known to improve processing of the melt and also to control glass solubility. The glass structure of phosphate glasses with 37 and 35 mol% P 2O 5 and addition of 1 to 10 mol% TiO 2 was analysed using 31P MAS NMR, and the influence of structural changes on solubility, thermal properties, processing window and crystallisation behaviour was investigated. Glasses showed an increase in activation energy for crystallisation with increasing TiO 2 content, resulting in an increased processing window, thereby allowing for fibre drawing and sintering of porous scaffolds. Deconvolution of 31P MAS NMR and calculation of network connectivity and average chain lengths suggest that Ti is acting as a network modifier with Ti 4+ units acting as ionic crosslinks between phosphate units thereby impeding crystallisation as well as chain hydration and subsequent chain dissolution.

Study on the protection of Er-doped phosphate glass waveguide surface in ion-exchange processing

A novel method, sputtering K9 glass film, is proposed to solve the surface corrosion of Er-doped phosphate glass during ion-exchange processing for optical waveguide fabrication. The corrosion causes are analyzed to be the intrinsically weak stabilization of phosphate glass structure, hydrophile and weakly acidic property of phosphate radical. Experimental results show that the K9 glass film could not only protect the Er-doped phosphate glass surface from being corroded but also give no influence on the waveguide fabrication. The effect of thickness of K9 glass film on the optical property of waveguide is also investigated and the optimal thickness is found to be 60–80 nm. It provides a good base for further fabrication of active phosphate glass optical waveguide devices.

Phosphate glasses for GRIN structures by ion exchange

Abstract Phosphate glasses were treated as a material for GRIN-lens production by silver-alkaline ion exchange. Glass durability (in salt melts) known to be a general obstacle for using these glasses in ion exchange technologies was found to profoundly increase in the sequence of meta ⇒ piro ⇒ orthophosphate. It is supposed to be due to the structure of phosphate glasses, which transforms in this sequence from 1D to 3D space arrangement of the glass-forming network. Ion exchange properties of these glasses were studied as well, and the maximal index variation in sodium–silver ion exchange was found to be 0.17.