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The viscosity and the shear relaxation behavior of supercooled Ag- and Sn- metaphosphate liquids are measured using parallel plate techniques. The fragility index m of these liquids, when taken together with that of other metaphosphate liquids, shows variation over a rather large range spanning from ~30 to 90 and is found to be a sensitive function of the strength and extent of connectivity or coupling between the phosphate chains provided by the modifier-oxygen coordination polyhedra. The high fragility of the Ag-metaphosphate liquid (m ≈ 90) is a result of the weak inter-chain coupling which is manifested in a polymer-like rheological behavior that is in contrast with the network-liquid like behavior of the metaphosphate liquids with lower fragility.

[EN] The glass forming ability of inorganic substances has traditionally been evaluated in kinetic terms related to the rate of spontaneous crystallization of their melts, which is related to viscosity from the macroscopic point of view. However, differences or similarities between the local structures of glasses and crystals of the same composition could have an additional influence on the kinetic ability to form a stable glass or a crystal from a melt. In this work, the local structure of alkali metaphosphate glasses and crystals has been analyzed by means of P MAS-NMR to demonstrate that the ability to form a glass is directly related to the differences between the atomic organization in the glassy states and the structure of the stable crystals at lower temperatures. This implies that chemical compositions having a similar atomic order in their glass and crystal structures will not easily develop the disordered long-range structure of glass., Agencia Estatal de Investigación/FEDER) MAT2017-87035-C2-1-P. The authors are thankful to G. Tricot from the University of Lille (France) for the acquisition of part of the NMR spectra.

Bulk glasses of the compositional series (A) xNb2O5–(50-x)ZnO–50P2O5 and (B) xNb2O5–50ZnO-(50-x)P2O5 were prepared to investigate possible substitution of cation (Zn2+), series A, and anion (PO3−), series B, with niobium and the effect of this substitution on the structure, density, molar volume, glass transition temperature and coefficient of thermal expansion. The structure was studied by Raman and 31P MAS NMR spectroscopies. The chemical model, based on the idea of chemical compounds as components with the lowest Gibbs energy and therefore the most stable, and on the results of 31P MAS NMR spectroscopy, was proposed for series B. It was found that niobium acts in glasses of series B only as a cation NbO3+, unlike the original idea of forming an anion of NbO−, that is, similarly to series A, where it replaces the cation. This leads to a change in the metaphosphate network of series B to the network that is similar to series A glass. The validity of this idea was verified by experimentally obtained compositional dependencies of molar volume, glass transition temperature and thermal expansion coefficient. Changes observed in thermal measurements indicate the evolution of a more rigid structure and more intensive cross-linking of the phosphate chains with increasing content of niobium.

Phosphate glasses are of great interest for basic research and for special applications in various fields as technical and optical glasses. Metaphosphate compositions with PO4-chain structure are mostly used. The cations have a significant effect on the properties of the glasses and melts. This was studied in more details. High purity metaphosphate glasses, Mn(PO3)n with M = Na+, K+, Zn2+, Mg2+, Ca2+, Sr2+, Ba2+, Al3+ and Fe3+, were prepared and the optical and thermal properties were measured with different methods. The electrical conductivity of glasses and melts is the property of great practical importance. It was determined by impedance spectroscopy in a wide temperature range from 300 to 1250 °C in frequency range of 0.1 Hz to 6 MHz. The electrical conductivity of alkaline earth phosphate glasses and melts increases with increasing ion radius of the cation. NaPO3 and KPO3 glasses and melts have much higher conductivity. Viscosity measurements were carried out from transformation temperature, Tg, to the melt. The measured data were fitted and the activation energies of the conductivity and viscosity were calculated. Simple exponential behavior was found at temperatures below Tg, but above Tg only in very narrow temperature range. The relation between conductivity and viscosity was considered.

A new melt derived glass system consisting of Co2O3 added to 40P2O5·25B2O3·25CaO·10Na2O matrix was investigated in order to evaluate the influence of cobalt ions on the network structure. Multiple techniques, i.e. X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the local structure, the nature of the chemical bonding and the surface composition of these samples. The XRD measurements proved the vitreous character of samples with 0 and 3 mol% Co2O3. At higher cobalt oxide content (5, 7 and 10 mol%) the occurrence of a crystalline phase characteristic to Co2P4O12 has been observed. The complementary spectroscopic studies (FTIR and Raman) revealed that the incorporation of Co2O3 enhances the network connectivity and thereby the short range order in samples. Depending on their amount, the cobalt ions differently influence the borophosphate network via the tetraborate/triborate and metaphosphate/pyrophosphate ratios. For the sample containing 10 mol% Co2O3 the FTIR analysis indicates absorptions assigned to vibrations in CoO6 tetrahedra and suggests the presence of six-coordinated cobalt ions in Co3 + valence state. This study has proven that borophosphate based glasses are able to entrap cobalt ions, are sensitive from structural point of view to the amount of Co2O3 and possess interesting structural peculiarities.

Modifier-mixing provides a useful tool for tailoring the structural dynamics of oxide glasses. Its physical basis, however, remains subject to intense discussion. Here, we extend our previous consideration of Ca-Mg mixing in alkaline earth metaphosphate glasses [J. Non-Cryst. Solids 468, 74–81 (2017)] across the broader range of alkaline earth species. We report on the effects of divalent modifier mixing for pairs selected from the group of Mg, Ca, Sr and Ba. For this, short-range structural features as obtained from nuclear magnetic resonance, Raman and far-infrared spectroscopy are related to various physical properties, including ionic mobility. Depending primarily on the difference in ion size and bond localization among the modifier cation species, we find different extents of the mixed-modifier effect. This agrees with the dynamic structure model in which the mismatch of cation sites governs non-linear mixing effects.

The O2− anions coordination by 3-5 of Mg2+ cations is the origin of Mg-rich cluster formation and photoemission properties of magnesium metaphosphate glasses. XRD, SAED and TEM analyses exhibit that Mg-rich clusters are of amorphous structure. The replacement of MgO by Fe2O3 results in the formation of crystalline Fe-rich regions. FTIR spectra reveal that Fe2O3 acts as network former and/or modifier by forming FeO4 and/or FeO6 groups, respectively. EDX mapping reveals that these Mg-rich clusters are disappeared at the expense of iron-rich clusters formation. UV-Vis absorption and fluorescence spectroscopies demonstrate that such coordination behavior is the reason for the photoemission of presented magnesium phosphate amorphous structure. Furthermore, replacement of Fe2O3 by MgO leads to photoemission quenching, which is assigned to the formation of Fe-rich clusters.

The effect of modifier mixing on structure and properties of (Ca, Mg) metaphosphate glasses is considered across the binary join of xMgO-(1-x)CaO-P2O5. Pronounced extrema in hardness, Young's modulus, local creep and glass transition temperature are related to variations in modifier precipitation. Both alkaline earth species compete for octahedral lattice sites, what leads to an increase in the fraction of [MgO4] tetrahedral units at equimolar mixing. At the same time, the structural backbone of phosphate Q2 species is affected through favorable formation of ring- and chain-like superstructures in the presence of Ca2 + and Mg2 +, respectively.

A melt-quenching method is used to prepare homogeneous glasses inside the 20Li 2 O-(50-x)Li 2 WO 4 -xTiO 2 -30P 2 O 5 (x = 0, 5, 8, 10 and 15 mol%) system. The amorphous and glassy states of the glasses are evidenced by the X-ray diffraction and differential scanning calorimetry (DSC) analysis, respectively. The glasses were found to be colorless. The determined parameters for the glasses such as density, molar volume and glass transition temperature ( T g ) depend strongly on the chemical composition of the glasses. The density and T g are found to decrease and increase with TiO 2 content, respectively. Infrared (IR) spectroscopy is used to characterize their structural approach. This technique has allowed the identification of different phosphate structural units mainly pyrophosphate and metaphosphate in their structure. From the absorption edge studies, the values of the optical band gap, E g , and Urbach energy, ΔE, were evaluated. The optical band gap is found to depend on the glass composition and it decreases as the content of the TiO 2 increases.

Modifier-mixing provides a well-established tool for generating non-linear trends in physical properties of multi-component glasses. While typically, mixtures of alkali or alkaline earth ions are considered, here, we report on the structural incorporation of Co 2 + and Mn 2 + , respectively, in strontium metaphosphate glasses, and on the associated Co-Sr/Mn-Sr mixed-modifier effect. Structural variations in the short and intermediate range were investigated with vibrational spectroscopy and synchrotron X-ray diffraction, elucidating the coordination states of the two transition metals as a function of mixing ratio. For the join of Co-Sr, we find that the octahedral coordination dominates for lower contents of cobalt, whereas the tetrahedral state is predominantly found at higher cobalt concentration. The analogue decrease in the coordination number is weaker when mixing manganese and strontium ions. Coordination numbers are shown to correlate clearly with vibrational spectroscopic data and macroscopic physical properties.

Zinc and barium metaphosphate glasses containing dopants of MnO2 (2, 4, 8%) were prepared. Collective studies were carried out through optical, photoluminescence and Fourier transform infrared (FTIR) spectral measurements for the prepared glasses before and after gamma irradiation. Electron spin resonance (ESR), thermal expansion and crystallization studies were also investigated. Optical spectra for undoped and MnO2–glasses reveal strong ultraviolet (UV) absorption due to trace iron impurity in the materials used for preparation of glasses and Mn2 + ions are not identified due to spin–forbidden nature of their spectra. Upon gamma irradiation, the MnO2–doped glasses reveal extension of the UV absorption exhibiting two peaks together with the generation of an induced broad visible band centered at 570–580 nm. Extra two glasses doped with 8% MnO2 were melted under reducing condition and they showed characteristic band at 410 nm related to Mn2 + ions absorption. Photoluminescence (PL) spectra reveal two excitation peaks in MnO2–doped zinc phosphate glasses at 348 and a sharp peak at 410 nm while the MnO2–doped barium phosphate glasses exhibit a sharp peak at 410 nm and a curvature at 348 nm. The emission spectra show a broad band centered at 620 nm in both glasses but with a curvature at 605–610 nm in zinc phosphate glasses which are correlated with the transition 4T1g → 6A1g.The efficiency of the photoluminescence increases with the MnO2 content and the heat treatment. The values of the optical band gap (Eopt) and Urbach energy (∆ E) were calculated. FTIR spectra reveal vibrational bands due to phosphate network mainly of metaphosphate groups but in zinc phosphate glasses, the mid spectra show compact network because of the ability of Zn2 + ions to participate partly as ZnO4 or P–O–Zn linkages. Thermal expansion data show different responses. Zinc phosphate glasses show anomalous behavior related to the change in the coordination of zinc cations while barium phosphate glasses exhibit normal expansion because Ba2 + ions exist only as modifiers. The crystallization behavior reflects also anomalous behavior. The zinc phosphate glass crystallizes in two crystalline species, mainly zinc metaphosphate phase and another zinc phosphate (3ZnO·P2O5) phase while the barium phosphate glass crystallizes only in barium metaphosphate phase.

Glasses with composition xGa2O3–(50-x)ZnO–50P2O5 (where x = 0–30) were prepared, and their basic physical characteristics (density, molar volume, glass transition and softening temperatures, thermal expansion coefficient and microhardness) were measured and discussed in connection with structural changes. Raman spectroscopy and 31P MAS NMR showed that increasing substitution of zinc(II) by gallium(III) shifts the basic structure of the glass from the prevailing metaphosphate (Q2) to pyrophosphate (Q1). With the highest content of gallium (x = 30), orthophosphates (Q0) appear, which ultimately leads to crystallization of GaPO4 in the glassy matrix. Therefore, glass with x > 25 could not be prepared, even with rapid cooling. 71Ga MAS NMR showed that at a lower Ga concentration, the dominating metaphosphate structure gallium was primarily six-coordinated, whereas with the dominating pyrophosphate structure (x ≥ 10), four-fold coordinated Ga prevailed.

We have sought the structural origin of the recently reported electrical conductivity of lithium copper phosphate glass system (50-x) Li 2 O-xCu 2 O-50 P 2 O 5 , as lithium oxide is gradually replaced by Cu 2 O. The structure of these glasses was determined by X-ray photoelectron spectroscopy, Fourier Transform Infrared Spectroscopy and Raman spectroscopy. The results show the presence of both mobile Cu + and relatively immobile Cu 2+ ions. The relative fraction of Cu 2+ [Cu 2+ / Cu tot ] and non-bridging oxygen increases with x; the latter indicating a tendency towards depolymerization of the network. On the other hand, there is enhanced crosslinking within the network as P O ⋯ Li bonds are replaced by relatively covalent P O ⋯ Cu bonds. This leads to a more cross-linked structure and a progressive reduction of the optimum sites for the jumping of both Li + and Cu + , in agreement with the observed increase of the energy barrier for ion transport as Li 2 O is replaced by Cu 2 O.

Oxynitride glasses are mixed-anion glasses, in which the oxygen atoms have been partially substituted by either two-fold (Nd) or three-fold (Nt) coordinated nitrogen atoms, introducing additional bonds and thereby constraining the glass network and enhancing the atomic packing density. Phosphate glasses are more prone to undergo nitridation via ammonolysis at relatively low temperature compared to other types of oxide glasses, but here the question is how the nitridation influences the glass transition, structure, and dynamics in phosphate glasses. Here, we answer this question by taking sodium and lithium metaphosphate oxynitride glasses as model systems. Using differential scanning calorimetry (DSC), we measure the effect of the atomic nitrogen/phosphorus (N/P) ratio on the glass transition temperature (Tg), jump in isobaric heat capacity at the glass transition (ΔCp), glass transition width (ΔTg), and liquid fragility index (m) of these model glasses. The results show that the nitridation causes an increase in the atomic packing density and Tg. In addition, ΔTg increases and m decreases with increasing N/P, both implying that the liquids become stronger upon nitridation, whereas ΔCp does not vary systematically with N/P within the error range. We discuss the origin of these changes in terms of the underlying changes in the short- and intermediate-range order structures, as detected by Raman spectroscopy.

MgO–CaO–P2O5–Nb2O5 glasses with the substitution of MgO for CaO consisting predominantly of meta-, pyro-, and orthophosphate groups were prepared using a melt-quenching method, and their structures and dissolution behaviors were investigated. Magnesium in the metaphosphate compositions was shown to act as a modifier oxide and coordinate phosphate groups. Magnesium in the pyro- and/or orthophosphate compositions was shown to act as a network former and to form P–O–Mg bonds, which crosslink short phosphate groups. The chemical durability of the metaphosphate glasses increased with increasing the substitution of MgO for CaO because magnesium exhibits a larger field strength than calcium. However, the durability of the pyro- and/or orthophosphate glasses decreased with increasing the MgO content: P–O–Mg bonds weakened the glass network structure and induced hydrolysis.

Ternary phosphate glasses of the system (ZnO)(0.45 − x)–(P2O5)(0.55 − y)–(V2O5)z, (y = 0; x = z = 0.01, 0.1; 0.2) and (x = 0, y = z = 0.1; 0.2) are prepared via the sol–gel process using zinc acetate, ammonium metavanadate and phosphoric acid as precursors. Spectroscopic investigations reveal a phosphate glass system depolymerization by systematic conversion of PO3− metaphosphate chains into (P2O7)4 − pyrophosphate, with the formation of P–O–V and V–O–V bonds, which replace P–O–P ones. Heat treatment of the dried xerogels containing 10% of V2O5 at temperatures 400–600 °C shows a similar trend in their infrared spectrum then that of glass obtained by melt quenching at 1000 °C. Inhibitive effect of the glass composition (ZnO)0.45–(P2O5)0.45–(V2O5)0.1 obtained at 600 °C and 1000 °C in simulated water was studied by electrochemical impedance spectroscopy (EIS). Inhibitory efficiency for both samples is the same ~ 95%.

In order to understand how the B2O3 insertion alters the structure and properties of the widely used zinc metaphosphate glass composition, advanced 1D/2D solid state MAS-NMR techniques were applied in this contribution to B2O3-Zn(PO3)2 glasses. High field (18.8 T) 1D NMR experiments allowed for a detailed characterization of the borate local order but did not provide much information about the phosphate speciation. We show how a set of 2D correlation NMR techniques could be applied to obtain additional data. First, 11B 2D DQ-SQ NMR spectra were edited to monitor the formation of the borate network through [x]B O [x]B linkages. In a second time, 11B(31P) D -HMQC technique was applied to characterize the formation of [x]B O P bonds and to provide additional information used to decompose the 1D 31P MAS-NMR experiments. This first 1D/2D NMR analysis of the B2O3-Zn(PO3)2 line was finally used to construct a structural model which shed light upon the glass transition temperature non-linear evolution.

To study the binding possibilities of Zn2+, Ca2+ and Cu2+ ions in the glassy phosphate network, metaphosphate glasses of xZnO-(50-x)CuO-50P2O5 and yCaO-(50-y)CuO-50P2O5 systems were prepared across the entire composition lines. Using Raman spectroscopy, 31P MAS NMR, electron paramagnetic resonance (EPR) and differential scanning calorimetry (DSC), it was found that zinc and copper are both four times coordinated and interact with donor oxygens in the same phosphate chain, calcium is six times coordinated and crosslinks phosphate chains significantly increased by this the glass transition temperature. It was further found that all copper-containing glasses are phase separated, which is also clearly reflected, in addition to the 31P MAS NMR and EPR spectra, in the compositional dependence of the glass transition temperature. The experimental results obtained by all the techniques used are discussed in detail.

Herein, diamagnetic PbO–Bi2O3–B2O3–Al(PO3)3 glasses are prepared by melt-casting and the influence of phosphorus tetrahedral on the structure and optical properties of the glass has been systematically investigated. Compared to diamagnetic PbO–Bi2O3–B2O3 (PBB) glasses, the original boron chain network has been replaced by the boron-phosphate structure. The metaphosphate forms [PO4] units and expands the glass network, which leads to the decline of density and the increase of refractive index (up to ~2.423 @633 nm). The improvement of the magneto-optical properties performs in that the Verdet constant achieves 0.203 min/G cm at 633 nm and higher magneto-optical figure of merit displays a better optical performance than the diamagnetic glass without metaphosphate.

A zinc phosphate invert glass consisting of orthophosphate and pyrophosphate groups, with a composition of 65ZnO–30P2O5–5Nb2O5 in mol%, showed antibacterial activity that provides biological safety owing to its well-controlled Zn2+ ion-releasing behavior. In the present work, in order to fundamentally understand the possibility of using bio-functional coating on dental implant surfaces, a glassy thin film was deposited on silica glass or a metallic titanium substrate by radiofrequency magnetron sputtering using the 65ZnO–30P2O5–5Nb2O5 glass as the target material. The resultant coating was an amorphous thin film consisting of orthophosphate and pyrophosphate groups with a trace amount of a metaphosphate group. Although the amounts of orthophosphate and pyrophosphate groups in the film were smaller and larger, respectively, than those in the target glass, the condensation of these phosphate groups could be controlled to a trace amount even during the deposition. The thin film showed effective antibacterial activities against Gram-negative and -positive bacteria without cytotoxicity to osteoblast-like cells. The thickness of the film after being soaked in a Tris buffer solution reduced gradually with a ratio of ~10 nm/d; thus, it showed a relatively-high durability.

Mechanical properties and structure of melt-quenched ternary barium phosphate glasses belonging to the composition (50 − X)BaO–XCaF2–50P2O5 (X = 0 to 10 mol%) were studied using Vickers indentation and vibrational spectroscopy. Elastic moduli of prepared samples were calculated using the Makishima and Mackenzie (M–M) model. Density of glasses was measured using the Archimedes method, while molar volume and atomic packing density were calculated from measured density to study structural changes in the glass matrix. Vickers hardness and brittleness increased and fracture toughness decreased with increase in CaF2 content. This can be attributed to increase in the compactness of phosphate bonds and reduction in the molar volume of glasses with partial substitution of Ba2 + with Ca2 +. Infrared and Raman spectroscopies revealed that the glass network mainly consisted of metaphosphate units arranged in chain and ring structures together with small amounts of ultraphosphate and pyrophosphate units.

Fluoride–phosphate (FP) glasses have been developed (in terms of glass forming ability) as a more stable alternative to fluoride glasses. Benefitting from the low polarizability of the fluoride anion, high electronic band-gap and low phonon energy, they present one of the most important host species for the inclusion of rare-earth and other optically active dopants into fiber and bulk glass. A major limitation, however, has been the mechanical performance of these glasses and their susceptibility to damage and fracture. Here, we provide comprehensive data on elasticity, plasticity and fracture of a series of mixed fluoride–phosphate glasses with strongly ionic bonding character, spanning the compositional join of strontium metaphosphate and alkaline earth aluminum fluoride. Simplistic models such as that of Makishima and Mackenzie can reproduce the mechanical properties of these glasses within a limited compositional range. This break-down is explained in the context of glass structure, in particular, the role of intermediate VIAl3 + species which act as bridges between the fluoride and the phosphate sub-networks. A simple binominal model is implemented to estimate the atomic fractions of aluminum as well as of magnesium cations, which are linked to two or more phosphate units, and used as an indicator for the connectivity between the anion sub-networks. Such adjustment of the Makishima–Mackenzie model provides an unambiguous rational for the elastic properties, but also for the susceptibility to inelastic deformation and fracture of FP glasses.

Common phosphate glasses—for example, those in the metaphosphate region—show potential as biodegradable materials. Some applications, such as biocompatible thin films coated on titanium or its alloys using radiofrequency magnetron sputtering methods, require films with good chemical durability. In the present work, CaO–P2O5–TiO2/Nb2O5 glasses with a Ca/P ratio of ≥ 1.00 were prepared using a melt-quenching method, and their structures and dissolution behaviors were investigated. When the Ca/P ratio was increased, the amount of orthophosphate (Qp0) group in the glasses increased, and that of pyrophosphate (Qp1) group decreased. The amount of Qp0 group was greater than the amount of Qp1 groups in glasses with a Ca/P ratio of ≥ 1.14. Intermediate oxides (i.e., TiO2 and Nb2O5) in the glasses cross-linked with the phosphate groups to form P–O–Ti/Nb bonds; these bonds were expected to take a tetrahedral form. The glasses prepared in the present work showed excellent chemical durability, because of the P–O–Ti/Nb bonds and the delocalized P O bonds that resulted from the increasing Qp0 content in the glasses.

The experimental viscosity data of a series of alkali, alkaline earth and zinc metaphosphate glasses have been analysed using Vogel–Fulcher–Tamman, Avramov–Milchev and Mauro–Yue–Ellison–Gupta–Allan models. The kinetic fragility and activation energy for viscous flow have been obtained and studied as a function of the composition, paying special attention to the short and intermediate range order structure as studied by Nuclear Magnetic Resonance and Raman spectroscopy. The fragility shows an increasing tendency within the alkali and alkaline earth series and presents the lowest value for the Zn(PO 3 ) 2 composition. Meanwhile the modifiers influence on the local structure of the PO 4 tetrahedra follows a direct relationship with their cationic potential; both static Nuclear Magnetic Resonance and Raman experiments showed evidence of a change in the rings versus chains configurations at the medium range order that could have an important contribution on the variation of activation energy. Furthermore, the molar volume and average bond strength of the glasses have shown to play a most important role, having a similar variation as the activation energy in the high viscosity range. However, the low viscosity range data seem to increase with the modifier's cationic potential, thus suggesting a different flow mechanism when compared with the high viscosity range.

Copper based oxide glasses are especially interesting for the possibility of ionic-electronic mixed conduction, which has potential applications in energy and switching devices. Accordingly, lithium metaphosphate glasses are investigated within the (100-x) Li 2 O - xCu 2 O - 50P 2 O 5 series, where Li + ions are gradually replaced by copper ions. Based on the changes in glass transition temperature and thermal stability via structural modification, the glasses are shown to be predominantly ionic conductors. In fact, they exhibit signs of classic mixed mobile ion effect (MMIE), a hallmark of ion conduction in glass, which would be due to Li + and Cu + ions in the present case.

A new optical glass with the molar composition 20B2O3-50P2O5-10Li2O-9Al2O3-5ZnO-3Dy2O3-3Tb2O3 was obtained by melting-quenching technique comprising wet route raw materials preparation, and the structural and optical characteristics of the glass were investigated by different experimental techniques. The amorphous nature was confirmed by X-ray diffraction (XRD) and the thermal stability was assessed by differential thermal analysis (DTA). Information about the defects of the co-doped glass as well as about the elemental compositional homogeneity was revealed by scanning electron microscopy/energy dispersive spectrometry (SEM/EDS). Structural information provided by Fourier Transform Infrared (FTIR) and Raman spectroscopy indicated metaphosphate structure of the glass together with boron oxide mostly in [BO3] Q2 units and also P O B bonds. Ultraviolet–visible (UV–Vis) absorbance, photoluminescence (PL), photoluminescence excitation (PLE) and time resolved photoluminescence (TRPL) spectra and luminescence decay curve were investigated systematically. Energy transfer process between Dy3+ and Tb3+ ions and its influence on luminescent properties were discussed.

Phosphate glass with a high transmission level in the visible and near-IR spectral regions doped with a high cerium concentration (up to 25 mol%) was synthesized and experimentally investigated in terms of applicability as a material for magneto-optical devices. Glass transition temperature was 590 °C. Glass refractive index varied between 1.5831 and 1.5884 depending on cerium content. The structure of the glass obtained was mostly metaphosphate with admixture of ultraphosphate complexes. It is shown that the maximum values of Verdet constant (11 rad/T/m at 1064 nm) are reached with increasing cerium concentration up to 25 mol%. The analysis proves the viability of the studied glass to create optical elements using the Faraday effect.

xMoO3-50ZnO-(50-x)P2O5, i.e. (1-x/50)Zn(PO3)2-(x/50)ZnMoO4, glasses were prepared up to x = 25. It has been proved that the glasses are not a mixture of boundary components, but that chemical reactions taking place in the melt during synthesis produce in equilibrium a more complicated chemical mixture. Molybdenum is incorporated into the glass structure as a molybdate(2-) and also as complex cations, a colorless molybdenyl MoO4+ (d0 system) and blue colored MoO3+ (d1). The chemical model of the studied glasses was designed indicating that the glassy matrix gradually changes with increasing molybdenum content from pure anionic metaphosphate to the cationic-anionic network with the help of molybdenyl cation strongly bonded by four covalent donor-acceptor bonds with non-bonding phosphate oxygens. The compositional dependencies of some physical properties agree with the proposed chemical model. The melts or glasses of chemical compositions near the glass-forming border are less stable and immiscibility of glass phases was found.

Many phosphate glasses dissolve in aqueous solutions, and they are increasingly studied for use as degradable biomaterials. As magnesium has been suggested to improve glass formation in phosphate glasses, its effect on glass structure, thermal properties and dissolution were studied. Two phosphate glass series (one in the metaphosphate range with 50 mol.% P2O5 and one invert series with 30 mol.% P2O5) in the system P2O5-CaO-TiO2, where calcium was partially (0 to 100% on a molar base) replaced by magnesium, were produced by a melt-quench route. Substitution of magnesium for calcium reduced the glass density (owing to the lower atomic weight of magnesium compared to calcium), made the phosphate network more compact, and caused Raman bands to shift to higher frequencies. Magnesium substitution significantly improved the processing of the glasses in both series by widening the processing window. The solubility of both glass series was low as shown by negligible pH changes and low ionic concentrations, with less than 7.5% of ions being released over 1 week. There were no significant differences in the solubility of the two series, which is surprising as metaphosphate glasses are generally considered to be more soluble than invert glasses. Magnesium substitution had a marked influence on invert glass dissolution, increasing the solubility about three-fold compared to the calcium-containing glasses, while no such effect was observed for metaphosphate glasses. Results suggest that magnesium substitution affects metaphosphate glasses and invert glasses differently, but improves glass formation and processing in both.

We report on photoluminescence down-shifting and near-IR emission from Nd 3 + centers in 50P 2 O 5 –(50- x )SrO– x MnO metaphosphate glasses. In those glasses, manganese exists predominantly in its divalent state with a Mn 3 + fraction of less than 0.1 % of total Mn. The Mn 2 + ions are octahedrally coordinated so that a broad red emission band is observed after blue excitation. The emission peak red-shifts from 680 to 743 nm, the lifetime decreases from 14.5 to 1.7 ms and the internal quantum efficiency decreases from 36.5% to 2.5% with increasing Mn 2 + concentration due to concentration quenching, but luminescence activity can still be observed in the pure manganese metaphosphate. The absorption bands of Mn 2 + cover the broad region from 300 to 550 nm, which allows for the sensitization of Nd 3 + . Energy transfer from Mn 2 + to Nd 3 + occurs through a multi-phonon assisted non-radiative down-shifting energy transfer process. A decrease of the emission intensity and lifetime for VI Mn 2 + is observed after doping with Nd 3 + giving evidence for the energy transfer. A value of 89% is estimated for the maximum energy transfer efficiency.

Approximate glass forming region in the ZnO–Fe 2 O 3 –P 2 O 5 ternary system was determined. Structure and properties of two compositional series of x ZnO–20Fe 2 O 3 –(80 − x )P 2 O 5 (A series, x = 20–40 mol.%) and x ZnO–10Fe 2 O 3 –(90 − x )P 2 O 5 (B series, x = 20–55 mol.%) were investigated. Phase identification was conducted by X-ray diffraction. Structural studies were carried out by Raman spectroscopy. Aqueous durability was measured by the glass dissolution rate in deionized water at 90 °C. Thermal properties were measured by differential scanning calorimetry and thermal dilatometry. Samples with ≥ 60 mol.% P 2 O 5 can form glasses, whereas samples with ≤ 30 mol.% P 2 O 5 cannot form glasses. Glass forming ability increases with increasing ZnO/Fe 2 O 3 ratio for samples with fixed P 2 O 5 content which locates in the range of 35–60 mol.% P 2 O 5 . Glass structure varies from metaphosphate to pyrophosphate with increasing ZnO content in each series. The structure variation leads to increase in density, aqueous durability and glass transition temperature and decrease in thermal expansion coefficient and thermal stability. Further improvement in thermal stability of these glasses with excellent aqueous durability in A and B series may improve their suitability for low-to-mid temperature sealing applications.

The main objective of this work has been to prepare and characterize the thermal and structural properties of glasses in the pseudo binary system TeO 2 –Pb(PO 3 ) 2 with respect to the composition. Homogeneous and transparent glass samples were obtained by the melt-quenching method in a large glass forming range in the pseudo binary system (100 − x )TeO 2 – x Pb(PO 3 ) 2 with x varying from 5 to 100. Thermal properties investigated by DSC pointed out an increase of the glass transition temperature from x = 5 to x = 40 and further decrease of Tg for higher Pb(PO 3 ) 2 concentrations. A similar tendency has been observed for the thermal stability against devitrification measured using the stability parameter Tx–Tg. FTIR together with Raman spectroscopies allowed building a structural model for these glasses with the contribution of distinct phosphate and tellurite units depending on the composition. Identification of crystalline phases obtained after the glasses heat-treatments obtained by X-ray diffraction support the structural evolution suggested by vibrational spectroscopies. These data suggest that incorporation of TeO 2 in the lead metaphosphate glass results in tellurium conversion from TeO 4 seesaw geometry to TeO 3 trigonal pyramids and consequent conversion of well-known metaphosphate units Q 2 to modified pyrophosphate units Q 2 1Te in which the phosphorus PO 4 tetrahedron is linked to another PO 4 unit and one TeO 3 pyramid. These tellurite trigonal units cross-link the modified metaphosphate chains with a resulting increase of the glass network connectivity. For high TeO 2 concentrations, all Q 2 were converted to Q 2 1Te and the additional tellurium atoms are incorporated in the glass network as TeO 4 seesaw units with a glass network built from a tridimensional network of TeO 3 , TeO 4 and Q 2 1Te . Finally, this work pointed out the possibility to use this pseudo-binary system for the preparation of phosphate glass-ceramics containing a TeO 2 crystalline phase or tellurite glass-ceramics containing a pyrophosphate or metaphosphate crystalline phase.

Corner cracks were initiated in a series of lithium–magnesium-metaphosphate glasses with different Li-to-Mg ratios by performing Vickers indentation under humid conditions (RH = 50% and RH = 65%) and in dry nitrogen gas atmosphere (RH = 0.01%). Propagation of each crack was observed up to 240 h. Distinct condensation of water at the crack-tip up to 30 μm occurred in humid environments, which led to a decrease in open crack length, while in dry nitrogen gas atmosphere this phenomenon was absent. A square root of time dependence was observed for the crack-tip condensation (CTC) kinetics as well as for weight gain experiments on crack-free glass specimens. Slow crack growth and CTC were dependent on the Li-to-Mg ratio of the glasses and showed a negative deviation from a linear compositional trend. Deviation of CTC was largest for glasses of Li-to-Mg ratio > 2:1 indicating a mixed mobile ion effect beyond charge neutrality, while the fatigue resistance exhibited a maximum at concentrations of equal charge. On the other hand a positive deviation from additivity was found for hardness and Young's modulus indicating increased resistance against elastic and plastic deformation for glass compositions of mixed Li + and Mg 2 + ions.

The work deals with optical and structural properties of aluminophosphate glasses from Li 2 O–BaO–Al 2 O 3 –La 2 O 3 –P 2 O 5 system containing Sm 3 + and Eu 3 + ions. X-ray fluorescence (XRF) has been used to establish the elemental composition of these materials. The influence of Sm 3 + and Eu 3 + ions on the optical properties of these glasses has been investigated in relation with their structural characteristics. The optical behavior of these materials has been studied by ultra-violet–visible (UV–Vis) spectroscopy, revealing absorption maxima specific to the doping ions. Structural information via vibration modes was provided by Fourier Transform Infrared (FTIR) absorption spectra evidenced as P O P symmetrical and asymmetrical stretching vibration modes, P O P bend, PO 2 − symmetrical and asymmetrical stretching vibration modes, P O stretching vibration mode and P O H water absorbance. Raman spectra acquired by 514.5 nm laser excitation disclosed peaks specific to metaphosphate network. Information about the elemental compositional homogeneity of Sm 3 + and Eu 3 + -containing glasses as well as about the defects of the doped-glasses is revealed by scanning electron microscopy/energy dispersive spectrometry (SEM/EDS). Fluorescence spectroscopy measurements put in evidence important fluorescence peaks found at 596 nm and 643 nm for Sm 3 + ions in phosphate matrix and 611 nm and 700 nm in the case of Eu 3 + -doped glass.

Development of crystallization in the CaO–Al 2 O 3 –TiO 2 –P 2 O 5 system glasses was investigated in the presence of ionic and metallic silver. Differential thermal analysis, X-ray diffractometry, ultra violet–visible spectrophotometry, atomic force microscopy and scanning electron microscopy were used to evaluate the resulted glasses and glass-ceramics. It was found that silver ions facilitated crystallization by decreasing the viscosity of the glasses. However, metallic silver, which was formed through heat treatment in hydrogen atmosphere, improved heterogeneous crystallization of the reduced glasses in the subsequent heat treatment. The preformed metallic silver led to effective crystallization of calcium titanium phosphate (CaTi 4 (PO 4 ) 6 ), calcium metaphosphate (Ca(PO 3 ) 2 ) and calcium pyrophosphate (Ca 2 P 2 O 7 ) phases at significantly decreased temperatures. The two latter phases were partially dissolved out by leaching in acidic solution and left out a porous structure of calcium titanium phosphate glass-ceramic.

Electron paramagnetic resonance (EPR) and fluorescence spectroscopy are sensitive and selective methods for probing coordination and bonding of Mn2+ ions in glasses. Both methods provide additional information on Mn–Mn ion interactions and cluster formation. Mn2+ was found to be tetrahedrally coordinated in boro-silicate glasses of high optical basicity, and octahedrally coordinated in low alkaline boro-silicate glasses (duran-type) as in fluoride-phosphate glasses. Broad emission bands and multicomponent fluorescence decay curves in duran glasses indicate very strong Mn–Mn ion interactions and the presence of multiple Mn2+ sites. Site distribution is more homogenous in metaphosphate glasses, though concentration quenching is apparent at high Mn-levels. As the Mn-content increases the EPR spectra show exchange narrowing due to a decrease in the Mn–Mn distances in the duran series, but show extreme linewidth broadening due to increased cluster sizes at constant Mn–Mn distances for metaphosphate glasses. For the fluoride-phosphate and boro-silicate systems investigated, fluorescence lifetimes are found to decrease as the wavelength of the emission maximum increases and with increasing g-values of the sextet at g = 2. For octahedral coordination of Mn2+ ions the EPR hyperfine splitting constant decreases linearly with increasing optical basicity, as a result of an increasing covalent character of the Mn2+–ligand bond.

Radiation-induced defects generated by successive gamma irradiation have been investigated in V 2 O 5 -doped phosphate glasses of three basic compositions, namely, sodium metaphosphate, lead metaphosphate and zinc metaphosphate. Glasses were prepared from chemically pure materials. Melting was carried at 900°–1100 °C for 1 h and with several stirrings of the melt to achieve homogeneity. The glassy samples were annealed at 200°–250 °C and left to cool to room temperature at a rate of 20 °C/h. Polished samples from undoped and V-doped samples of equal thickness. ~ 2 mm were measured in a double beam UV–visible spectrophotometer at 200–1000 nm before and after gamma irradiation. Induced defects were analyzed for these three phosphate glass systems. Infrared absorption spectra were measured for the prepared undoped and V-doped samples by the KBr technique before irradiation and after being subjected to a high dose of 7 M Rads (7 × 10 4 Gy). The cumulative effects of gamma irradiation on the UV–visible spectra are correlated with the intrinsic and extrinsic defects within the various three glasses. Some shielding behavior for the various glasses towards successive gamma irradiation are observed and realized in relation to the different partner anions studied. The effect of gamma irradiation on IR spectra indicates the persistence of the main characteristic bands due to phosphate network and the minor changes are correlated with the possible changes in the bond lengths and/or bond angles of the building units during the irradiation process. The effect of V 2 O 5 on the IR spectra is correlated with the depolymerization effect of the glass network.

The mixed alkali effect in x K 2 O-(30 − x ) Na 2 O-30P 2 O 5 -40ZnO was firstly observed. Density, DSC, DC electrical conductivity, chemical durability and IR have been carried out for x K 2 O-(30 − x ) Na 2 O-30P 2 O 5 -40ZnO glasses. The DC electrical conductivity was measured in the temperature range between 100 °C and T g . The strength of the MAE in T g , DC electrical conductivity, and activation energy has been determined. It is observed that the strength of MAE in DC electrical conductivity is less pronounced with the increase of temperature. The extremum of the glass transition temperature, the DC electrical conductivity, the activation energy, and the DR were observed along with the variation of K alkali ratio [K]/[K + Na] (alkali dosage is constant). The results showed that extremum was caused by the large energy mismatch for ions jumping between dissimilar alkalis' sites as Swenson's structural model suggested, generally shown as the K + vibration pathway blocking by the Na + due to the difference of ions' diameter. IR convinced the good correlation between MAE of x K 2 O-(30 − x ) Na 2 O-30P 2 O 5 -40ZnO system glasses and the origination of metaphosphate structure, secondarily pyrophosphate, and [ZnO 6 ] octahedral.

An array of different structural probes has been used to define the effect of adding Zn and Ti to a sodium-calcium phosphate glass. X-ray absorption spectroscopy at the Zn K-edge suggests that the Zn atoms occupy mixed (4- and 6-fold) sites within the glass matrix. X-ray diffraction reveals a feature at 2.03 angstrom that develops with the addition of Zn and Ti and is consistent with Zn-O and Ti-O near-neighbour distances. Neutron diffraction is used to resolve two distinct P-O distances and highlights the decrease in P center dot center dot center dot P coordination number from 2.0 to 1.7 as the Ti metal concentration rises, which is attributed to the O/P fraction moving away from the metaphosphate value of 3.0 to 3.1 with the addition of Ti. Other correlations, such as those associated with CaO(x) and NaO(x) polyhedra, remain largely unaffected. These results suggest that the network forming P center dot center dot center dot P correlation is most disrupted, with the disorder parameter rising from 0.07 to 0.10 angstrom with the additional modifiers. Zn appears to be introduced into the network as a direct replacement for Ca and causes no structural variation over the composition range studied.

Undoped and transition metals (TM 3d)-doped lead phosphate glasses were prepared. Ultraviolet–visible absorption spectra were measured in the range 200–1100 nm before and after successive gamma irradiation. Experimental results indicate that the undoped lead phosphate glass reveals before irradiation strong and broad ultraviolet absorption which is related to the co-sharing of absorption due to both trace iron impurities and lead ions (Pb2+). In the TM-doped glasses, characteristic absorption bands are obtained in both the UV and/or visible regions due to each respective TM ion in addition to that observed by the base undoped UV absorption. Gamma irradiation produces with the undoped glass a prominent induced ultraviolet broad band centered at about 300 nm originating mostly from the contribution of trace iron impurities and the visible spectra reveal markedly high shielding behavior towards successive gamma irradiation, due to the presence of both high content of heavy Pb2+ ions and the sharing of phosphate as a partner. With TM-doped samples, the observed induced bands are virtually varying and related to the type of the sharing TM ions. Infrared absorption spectra reveal in the undoped and TM-doped glasses characteristic structural phosphate groups mainly consisting of metaphosphate and pyrophosphate units. Transition metals are assumed to cause depolymerization of the phosphate glass network with different ratios but the changes in IR spectral data are limited due to the low doping level. Gamma irradiation of the samples is assumed to cause changes in the bond angles or bond lengths of the structural phosphate units within network as evident in the variation of the intensities of the IR bands.

The structure of La-based metaphosphate glasses modified with aliovalent alkaline earth elements (M = Ba, Ca, Sr), with P:(M + La) ratio kept approximately at 3, were analyzed using Raman and IR spectroscopy. Increasing the concentration of the alkaline earths monotonically decreased the glass density and glass transition temperature, and shifted some vibrational modes by as much as 40 wavenumbers. The Raman frequencies of the symmetric POP and the P O vibrations depended on the M/La ratio, but not on the type of alkaline earth addition; however, the type of alkaline earth cation significantly changed the symmetric PO2 vibration. The average cation-oxygen coordination number remained near ∼7 except for a slight decrease for high concentrations of Ca and Sr substitutions. The POP/PO2 intensity ratio increased with increasing alkaline earth content. The replacement of divalent elements for trivalent La in a metaphosphate glass structure was partially accommodated by incorporation of protons as charge compensating defects. The protons were found to be in close proximity to the divalent cations.

Following a theoretical determination of cluster-models for lithium metaphosphate glass, a theoretical method for the prediction of structural data such as radial and bond distribution functions is presented. These are calculated and compared to experimental data for this particular glass. Useful conclusions are drawn regarding the general use of molecular electronic structure methods for the determination of the structure of glasses.

Sub-critical crack growth in various kinds of metaphosphate glasses was investigated by using DCDC (Double Cleavage Drilled Compression) technique. The crack growth measurements were only being made in Region III, or in an inert environment. In order to evaluate intrinsic crack growth behaviors in Region III, crack propagation tests were performed in dehydrated heptane, and the crack velocity, v, was plotted as a function of the stress intensity factor, KI. Fracture toughness of glass was also estimated from a stress intensity factor at a given crack velocity. For binary metaphosphate glasses (50MO · 50P2O5, M = Zn, Mg, Ca, Ba), fracture toughness increases in the order of Mg > Ca > Zn > Ba. However, the slope of KI–v curve is almost unchanged. In the case of aluminum containing metaphosphate glasses, with increasing aluminum content, fracture toughness increases and the slope of KI–v curve becomes smaller, regardless of the type of divalent cations in glass. It is concluded that an addition of aluminum ions into metaphosphate glass results in both high toughness and easy fatigue. In addition, the structural role of aluminum ions on the intrinsic sub-critical crack growth is discussed in terms of the models of atomistic bond rupture.

Rare earth (RE) phosphate glasses, (R 2 O 3 ) x (P 2 O 5)1-x , commonly form with x < 0.3. As previously discussed by Hoppe, in this composition range Q 2 groups provide 6 O nb (non-bridging oxygens) per RE, but higher RE coordinations can occur if RE are bonded to O nb on Q 3 groups, or if RE-O nb -RE configurations occur (where Q" refers to a PO 4 tetrahedra with connectivity of n). The values of N RO and R RO from the majority of the previous diffraction and EXAFS studies of RE phosphate glasses have been surveyed. Overall, the experimental results for 0.18 ≤ x < 0.28 indicate RE coordination is from 6.5 to 7.0 for large RE, and slightly lower for small RE. For x≥ 0.23 this implies the occurrence of RE-O nb -RE configurations, as observed in recent diffraction studies. The experimental results for x≤ 0.15 indicate RE coordination is from 7.5 to 8, which can be attributed to RE bonding to On on Q 3 groups. RE coordination of 8 for x ∼ 0.15 requires 2 Q 3 groups (per RE) to be connected to Q 2 groups. Comparison with estimated connectivities between Q 2 and Q 3 groups indicate that chemically ordered Q 2 -Q 3 linkages are required. A recent MD model of a Tb metaphosphate glass has N Ro = 6, but includes Tb bonded to O nb on Q 3 groups and Tb-O nb -Tb configurations, because it has a broad Q" distribution.

Numerous phosphate glass systems with compositions covering the entire glass forming range have been examined by small angle Xray scattering. The experiments were carried out in a widely extended interval of s values between 0.055 and 31 nm � 1 . A small angle scattering effect was detected for all samples investigated with the exception of the aluminium metaphosphate glass. The small angle scattering recorded indicates the presence of two differently-sized heterogeneity regions of electron density. The small-scale heterogeneities are present in magnesium and zinc phosphate glasses only. Their size is about 1 nm diameter in the magnesium and about 2 nm in the zinc phosphate glasses. The species do not result from liquid–liquid phase separation. Examinations to extract information on the nature of these heterogeneity regions are described in detail. There is no fundamental knowledge on the large-scale heterogeneities established. The small angle scattering suggests that their occurrence is related to water contamination. Anomalous small angle X-ray scattering experiments of a series of zinc polyphosphate glasses and a strontium metaphosphate glass sample are performed to examine the distribution of the Zn or Sr atoms, respectively.

Anelastic spectroscopy (internal friction and the dynamic modulus) was measured by means of a torsion pendulum at 3–12 Hz, in the range of 100–300 K, for a KAP metaphosphate glass. Two thermally activated internal friction peaks appeared at ∼190 and ∼250 K. These peaks were attributed to the behavior of potassium ions (high temperature) and to hydrogen (low temperature). Dynamic modulus showed a gradual decrease with increasing temperature in the range studied for all compositions.

Ternary sodium–cobalt–phosphate glasses of the composition (50 − x )Na 2 O–50P 2 O 5 – x CoCl 2 with x varying between 0 and 15 mol% prepared by melt quenching have been characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) techniques. Thermal ( T g , T c ) and electrical properties have been investigated. Infrared spectra reveal the formation of metaphosphate glasses ( Q 2 tetrahedral units) with symmetric bridging oxygen (P–O–P) and non-bridging oxygen (P–O − ). The spectra also indicate the formation of P–O–Co bonds in the metaphosphate glasses that replace P–O − –Na + bonds. The results of thermal studies correlate with these FT-IR findings and support the formation of P–O–Co bonds and an increased cross-link density with increasing CoCl 2 . This results in enhanced chemical durability and increased T g and T c of the glasses. The electrical conductivity parameters upon changing the composition have been correlated with structural changes in the glass matrix.

Previous diffraction studies of the structures of rare-earth phosphate glasses (R2O3)x(P2O5)1−x are extended to glasses with smaller R3+ ions with R = Sm, Gd, Dy, Er, Yb, Y for x = ∼0.25 and with R = Nd, Sm, Gd for x = ∼0.15. Parameters for the P–O, R–O and O–O first-neighbor peaks were obtained by Gaussian fitting. P–P and R–P distances were estimated from the positions of peak maxima. Effects of residual silica or alumina contents present as a result of glass processing were taken into account for selected samples. The P–O coordination number, NPO, and the P–O, O–O, P–P distances are consistent with the presence of phosphate tetrahedra and are insensitive to the R species and the R2O3 content. Rare-earth coordination numbers, NRO, decrease from ∼8 to ∼6.5 when x is increased from ∼0.15 to ∼0.25. NOO and NPP decrease with increasing R2O3 content indicating the network disintegration. The numbers NRO of the metaphosphate glasses (x = ∼0.25) decreases from ∼7 to ∼6 when R is changed from La to Yb. This change is also indicated by the behavior of the R–O distances and by constant number densities of atoms. The decrease in NRO with increasing R2O3 content is due to the reduction in the number of terminal O (OT) available for coordination of the R3+ ions (six at metaphosphate composition). Especially for smaller R3+ ions sharing OT between two R sites is not favored. The decrease by ∼0.04 nm of the prominent R–R first-neighbor distance with a change of R from La to Yb at the metaphosphate composition is indicated by a shift to higher magnitude of scattering vector of the shoulder occurring in front of the first main diffraction peak.