Structure and properties of MoO3-containing zinc borophosphate glasses

ZnO–B₂O₃–P₂O₅ glasses doped with MoO₃ were investigated in the series (100?x)[0.5ZnO–0.1B₂O₃–0.4P₂O₅]–xMoO₃, where bulk glasses were obtained by slow cooling in air within the compositional region of 0 ? x ? 60 mol% MoO₃. The incorporation of MoO₃ into the parent zinc borophosphate glass results in a weakening of bond strength in the structural network, which induces a decrease in chemical durability and glass transition temperature. Raman spectra reflect the incorporation of molybdate groups into the glass network of the studied glasses by the presence of the polarized vibrational band at ≈976 cm^?1 ascribed to the MO_x symmetric stretching vibrations and the depolarized band at ≈878 cm^?1 ascribed to the Mo–O–Mo stretching vibration. The incorporation of molybdate units into the glass network results in the depolymerization of phosphate chains and the formation of P–O–Mo bonds, as reflected in Raman and ³¹P NMR spectra. According to the ¹¹B MAS NMR spectra, tetrahedral B(OP)_4?x(OMo)_x units are formed in the glasses, whereas only a small amount of BO₄ units is converted to BO₃ units in the MoO₃-rich glasses.     

Structure–property correlations in lead borate and borosilicate glasses doped with aluminum oxide

Glass samples from four systems: xPbO–(100?x)B₂O₃ (x = 30, 40, 50 and 60 mol%), 50PbO–yAl₂O₃–(50?y)B₂O₃ (y = 2, 4, 6, 8 mol%), 50PbO–ySiO₂–(50?y)B₂O₃ (y = 5, 10, 20, 30 mol%) and 50PbO–5SiO₂–yAl₂O₃–(45?y)B₂O₃ (y = 2, 4, 6, 8 mol%) were prepared by a melt-quench technique. Characterization of these systems was carried out using density measurements, UV–visible spectroscopy, differential scanning calorimetry (DSC), and ¹¹B and ²⁷Al magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR). Our studies reveal an increase in glass density with increasing lead(II) oxide concentration in pure lead borates and also with addition of silica into 50PbO–50B₂O₃ glass. ¹¹B MAS NMR measurements determine that the fraction of tetrahedral borons (N₄) reaches a maximum for the glass containing 50 mol% of PbO in the PbO–B₂O₃ glass series and that N₄ is sharply reduced upon adding small amounts of Al₂O₃ into lead borate and lead borosilicate systems. ²⁷Al MAS NMR experiments performed on glasses doped with aluminum oxide show that the Al³⁺ are tetra-, penta- and hexa-coordinated with oxygen, even without any excess concentration of Al³⁺ over charge-balancing Pb²⁺ cations. ^[5]Al and ^[6]Al concentrations are found to have unusually high values of up to 30%. The results of UV–visible absorption spectroscopy, DSC and density measurements support the conclusions drawn from the NMR studies, providing a consistent picture of structure–property relations in these glass systems.     

Spectroscopic properties and ab initio calculations on the structure of erbium–zinc-borate glasses and glass ceramics

Glasses in the (Er₂O₃)_x·(B₂O₃)_(60 ? x)·(ZnO)₄₀ system (0 ≤ x ≤ 15 mol%) have been prepared by the melt quenching technique. X-ray diffraction, FTIR spectroscopy, UV-VIS spectroscopy and ab initio calculations studies have been employed to study the role of Er₂O₃ content on the structure of the investigated glass system.X-ray diffraction and infrared spectra of the glasses reveal that the B–O–B bonds may be broken with the creation of new non-bridging oxygen ions facilitating the formation of Er–O–B linkages. The excess of oxygen can be accommodated in the network by the conversion of sp² planar [BO₃] units to the more stable sp³ [BO₄] tetrahedral structural units. The linkages of the [BO₄] structural units can polymerize in [B₃O₉]^? 9 cyclic trimeric ions which will produce the ErBO₃ crystalline phase. An increase of the efficiency corresponding to the ⁴I_15/2 state to ⁴I_11/2 state (4f–4f) transitions of Er^+ 3 ions was observed for the erbium oxide richest glasses.Ab initio calculations on the structure of the matrix network show the thermodynamic instability of the [BO₄], [ZnO₄] and [Zn₄O] structural units. Formation of three-coordination oxygens was necessary to compensate shortage of oxygens from zinc ions.     

Semi-quantitative analysis for FTIR spectra of Al2O3-PbO-B2O3-SiO2 glasses

A series of glass of the molar formula xAl₂O₃-(50-x)PbO-25B₂O₃-25SiO₂ with x:2.5–17.5 with step of 2.5 mol.% was prepared and measured for, density, molar volume and infrared absorption. A semiquantitative analysis of the IR spectra was performed. It was found that each oxide would contribute in density with a specific factor. The density factor related to PbO is markedly higher than that of the other two oxides represent the glass skeleton which means that the content of PbO is the main factor affecting the density. The depolymerization of the whole glass skeleton increases with increasing the content of Al₂O₃. There is a competition between the role of PbO and Al₂O₃ in changing the value of N₄ and the crosslinking of the glass network. The silicate network tends to be distinguished from the reminder of the whole glass network with increasing alumina. The IR band located near 700 cm^? 1 was suggested to be due to the vibrations of bridging oxygens between trigonal boron atoms. An essential change in the role of PbO in these glasses from glass modifier to glass former occurred around 12 mol.% Al₂O₃.     

Bond character,optical properties and ionic conductivity of Li2O/B2O3/SiO2/Al2O3 glass: Effect of structural substitution of Li2O for LiCl

A glass of composition (20 ? x)Li₂O–xLiCl–65B₂O₃–10SiO₂–5Al₂O₃ where 0 ? x ? 12.5 wt% is prepared using the normal melt-quenching technique. The optical constants and electrical conductivity and their correlation are investigated, furnished and discussed with the substitution of Li₂O for LiCl. The mechanism of the optical absorption and the calculated Urbach energy follow the rule of phonon-assisted transitions. The ionic conduction mechanism is determined by activation energy process. Substitution up to 10 wt% LiCl provides high ionic conductivity (1.9 × 10^?2 Ω^?1 m^?1) due to the high average electronegativity of LiCl which increases the polarizability of lithium ions. The small cation–anion distance approach confirmed the enhancement in ionic conductivity of LiCl containing glass compared to that of Li₂O. Due to the large size of Cl^? ions, there is an expansion of the lattice which in turn broadens the available path windows. For 12.5 wt% LiCl, anomalous density behavior is observed and a reduction in conductivity is occurred, σ = 5.4 × 10^?3 Ω^?1 m^?1. Owing to the model of bond fluctuation, the reduction is attributed to the increase in the alkali halide concentration which creates bottlenecks that hinder the motion of Li⁺ ions. The ionic conductivity character is strongly supported by the behavior of the glass ionicity factor, density, molar volume, refractive index, average boron–boron separation, molar refraction, metallization criterion and non-bridging oxygen concentration of the studied glass.     

Quantitation of sulfate solubility in borosilicate glasses using Raman spectroscopy

Raman spectroscopy is used here as an innovative technique to investigate sulfate content in borosilicate glasses. Using Raman spectroscopy after having heated the material, the evolution of sulfate amounts can be followed as a function of temperature, time and chemical composition of the starting matrix. The accuracy of this technique was verified using electron probe micro analysis (EPMA), on two systems of glasses (SiO₂–B₂O₃–Na₂O (SBNa) and SiO₂–B₂O₃–BaO (SBBa)) in order to compare the effect of alkaline or alkaline-earth elements on sulfur speciation and incorporation. To quantitate sulfate content with Raman spectroscopy, the integrated intensity of the sulfate band at 990 cm^?1 was scaled to the sum of the integrated bands between 850 and 1250 cm^?1, bands that are assigned to Qⁿ silica units. Calibration curves were then determined for different samples. The determination of sulfate contents with Raman spectroscopy analysis is possible with an accuracy of approximately 0.1 wt% depending on the composition of the glass. It mainly allows us to follow sulfate removal during the elaboration process and to establish kinetic curves of sulfate release as a function of the viscosity of the borosilicate glass.     

Structure and properties of potassium niobato-borophosphate glasses

Bulk glasses of the series (1 ? x)[0.5K₂O–0.1B₂O₃–0.4P₂O₅]–xNb₂O₅ with x = 0–45.7 mol% Nb₂O₅ were prepared by slow cooling in air and investigated by Raman, ³¹P, and ¹¹B MAS NMR spectroscopy. The incorporation of Nb₂O₅ into the parent borophosphate glass results in a substantial increase in the glass transition temperature and chemical durability of glasses. Raman spectra showed that Nb atoms form distorted NbO₆ octahedra, which are isolated at low Nb₂O₅ content, whereas at higher Nb₂O₅ content they form clusters. ¹¹B NMR spectra of the glasses revealed the interaction between Nb₂O₅ and BO₄ tetrahedral units, which results in a partial transformation of tetrahedral BO₄ units to trigonal BO₃ units and the formation of mixed B(OP)_4?n(ONb)_n units.     

Structural impact of iron ions on BaBiBO4 glasses: Spectroscopic and dielectric investigations

Transparent glasses of composition 10BaO.20Bi₂O₃.(70 ? x)B₂O₃.xFe₂O₃ (wt.%) where 0 ≤ x ≤ 2.0, were characterized by XRD and SEM. Physical, spectroscopic and dielectric properties were investigated. At higher dopant of Fe₂O₃, EPR results revealed that, the number of Fe³⁺ ions participate in the resonance is decreased by forming a new signal at g ≈ 3.015 due to increase of antiferromagnetic interaction of Fe³⁺ ions and/or formation of low spin Fe³⁺ ions in the glass matrix. With initial 0.5 wt.% doping of Fe₂O₃, less dense glass is formed with colloids of metallic Bi⁰ atoms. The absorption bands at 604 and 712 nm in F5 glass are ascribed to Bi⁰ and Bi⁺ radicals respectively. No characteristic Fe³⁺ absorption bands (spin-forbidden) are found. Fe²⁺ ions are increased at higher concentration of Fe₂O₃. Higher concentration of Fe₂O₃ is favorable for BO₂O^?, BO₃, BiO₆ and FeO₆ symmetry unit leads to low band gap and high Urbach energy. By doping of Fe₂O₃ the dielectric parameters like dielectric constant (ε′), loss (tanδ and ac electrical conductivity (σ_ac) are found to increase.     

Optical and thermoluminescence properties of R2O–RF–B2O3 glass systems doped with MnO

Alkali fluoroborate glass systems containing manganese cations have been thoroughly investigated in order to obtain information about the structural role of manganese in such glass hosts. The amorphous phase of the prepared glass samples R₂O–RF–B₂O₃:MnO (with R = Li and Na) was confirmed from their X-ray diffraction. From the infrared spectra of these glass systems it was concluded that the glass structure contains two group of bands; one due to trigonal BO₃ units and the second due to the tetrahedral BO₄ units. As manganese was introduced, replacing lithium or sodium, it acts as a network modifier and the intensity of the second group of bands increases at the expense of the first group of bands. The optical absorption spectra of R₂O–RF–B₂O₃:MnO exhibited two conventional absorption bands; one due to Mn²⁺ ions and the other due to Mn³⁺ ions. The ESR spectra of these glasses showed a six-line hyper-fine structure centered at g = 2.01 (due to Mn²⁺ ions) and another signal at g = 4.3 (due to Mn³⁺ ions). The intensity of optical absorption bands and the ESR signal due to Mn²⁺ ions decreases with increasing MnO concentration indicating the conversion of Mn²⁺ ions into Mn³⁺ ions in the glass network. The thermoluminescence studies on these glass systems showed a quenching of TL output with increase in the concentration of MnO. All the obtained results were discussed on the basis of the glass structure and the conversion of Mn²⁺ into Mn³⁺ ions with increasing concentration of MnO in the glass systems.     

Properties and structure of (1 − x)Li2O–xNa2O–Al2O3–4SiO2 glass systems

(1 − x)Li₂O–xNa₂O–Al₂O₃–4SiO₂ glasses were studied for the progressive percentage substitution of Na₂O for Li₂O at the constant mole of Al₂O₃ and SiO₂. The crystallization temperature at the exothermic peak increased from 898 to 939 °C when the Na₂O content increases from 0 to 0.6 mol. The coefficient of thermal expansion and density of these as-quenched glasses increase from 6.54 × 10⁻⁶ °C⁻¹ to 10.1 × 10⁻⁶ °C⁻¹ and 2.378 g cm⁻³ to 2.533 g cm⁻³ when the Na₂O content increases from 0 to 0.4 mol, respectively. The electrical resistivity has a maximum value at Na₂O · (Li₂O + Na₂O)⁻¹ = 0.4. The activation energy of crystallization decreases from 444 to 284 kJ mol⁻¹ when the Na₂O content increased from 0 to 0.4 mol. Moreover, the activation energy increases from 284 kJ mol⁻¹ to 446 kJ mol⁻¹ when the Na₂O content increased from 0.4 to 0.6 mol. The FT-IR spectra show that the symmetric stretching mode of the SiO₄ tetrahedra (1035–1054 cm⁻¹) and AlO₄ octahedra (713–763 cm⁻¹) exhibiting that the network structure is built by SiO₄ tetrahedra and AlO₄.     

Structure and properties of Sb2O3-containing zinc borophosphate glasses

ZnO–B₂O₃–P₂O₅ glasses formulated with Sb₂O₃ were investigated in the series 50ZnO–10B₂O₃–40P₂O₅ + xSb₂O₃ (x = 0–70 mol%). With increasing Sb₂O₃ content, the values of glass transition temperature decrease from 492 °C down to 394 °C. The dissolution rate of the glasses reveals a maximum for the glass with x = 15 mol% Sb₂O₃. Raman spectra with increasing Sb₂O₃ content reflect the depolymerisation of phosphate chains. Antimony at low Sb₂O₃ content forms individual SbO₃ pyramids manifested in the Raman spectra by a broad vibrational band at ∼520–690 cm⁻¹. In the glasses with a higher Sb₂O₃ content SbO₃ units link into chains and clusters with Sb–O–Sb bridges manifested in the Raman spectra by a strong broad band at 380–520 cm⁻¹. The ³¹P MAS NMR spectra with increasing Sb₂O₃ content reflect the depolymerisation of phosphate chains at low Sb₂O₃ content and only small changes in the PO₄ coordination at a high Sb₂O₃ content. ¹¹B MAS NMR spectra reveal a steady transformation of B(OP)₄ units into B(OP)_4−x(OSb)_x units, accompanied by the transformation of BO₄ into BO₃ units with increasing Sb₂O₃ content.     

Optical band gap and Raman spectra in some (Bi2O3)x(WO3)y(TeO2)100−x−y and (PbO)x(WO3)y(TeO2)100−x−y glasses

The glasses representing (Bi₂O₃)_x(WO₃)_y(TeO₂)_100?x?y and (PbO)_x(WO₃)_y(TeO₂)_100?x?y systems were prepared. The dilatometric glass-transition temperatures of examined glass samples were found in the region 383–434 °C, the coefficient of thermal expansion varied from 12 to 16 ppm/°C and the density ranged from 6.30₂ to 6.80₈ g/cm³. From the optical transmission measurements of thin glassy bulk samples prepared by a glass blowing, the optical gap values were found in the narrow region 3.21–3.36 eV. For the temperature interval 300–480 K, the values of the temperature coefficient of the optical band gap varied from 3.7 × 10^?4 to 5.24 × 10^?4 eV/K. It is suggested that Raman feature observed at around 350 cm^?1 can be assigned to an overlap of Raman bands attributed to WO₆ corner shared octahedra and to the following three atomic linkages: Bi–O–Te, Pb–O–Te and W–O–Te.     

Coordination structure of Li+ in concentrated aqueous lithium alaninate solutions

Time-of-Flight (TOF) neutron diffraction measurements with the ⁶Li/⁷Li isotopic substitution technique were carried out for aqueous 18 mol% lithium alaninate solutions in D₂O in order to obtain structural information on the interaction between Li⁺ and the amino acid molecule in the concentrated aqueous solution. The first-order difference function, Δ_Li(Q), was obtained from the difference between scattering cross sections observed for solutions involving dl-CH₃CH(ND₂)COO⁶Li and dl-CH₃CH(ND₂)COO⁷Li. The distribution function around Li⁺, G_Li(r), exhibits well resolved first and second peaks that are tentatively attributable to the nearest neighbor Li⁺ ⋯ O and Li⁺ ⋯ D interactions. However, the coordination number, n_LiD, estimated from the area under the second peak is found to be much larger than the value, 2n_LiO, evaluated from the first peak of the present G_Li(r). This implies that the nearest neighbor Li⁺ ⋯ alaninate ion interaction may contribute to the second peak. Structural parameters concerning the first coordination shell of the Li⁺ has been determined through the least squares fitting analysis of the observed Δ_Li(Q). It has been revealed that the Li⁺ is surrounded by 2.4(1) D₂O molecules and 2.3(2) alaninate ions with interatomic distances of r(Li⁺ ⋯ O_D2O) = 1.97(1) Å, r(Li⁺ ⋯ D_D2O) = 2.62(1) Å and r(Li⁺ ⋯ O_alaninate) = 2.38(1) Å, respectively.     

Refractive index behavior in phosphate glass from the view point of B3+ and Al3+ coordination

Higher refractive index and higher Abbe value were obtained simultaneously at B₂O₃/Al₂O₃ = 1 in the system of 65P₂O₅–xAl₂O₃–(20 ? x)B₂O₃–10CaO–5Li₂O, although the refractive index generally shows a positive correlation with the dispersion. We investigated the molar volume and the molar refraction by Lorentz–Lorenz’s formula and also studied the coordination number of ¹¹B and ²⁷Al by MAS NMR. By the replacement of Al₂O₃ with B₂O₃, the molar refraction constantly decreased, but the molar volume was minimized at B₂O₃/Al₂O₃ = 1. The refractive index behavior of the glasses was mainly determined by the molar volume in the system. The coordination number of B³⁺ was only IV and it did not change if the composition was changed. On the other hand the coordinations IV, V and VI were observed for Al³⁺. The ratio of Al³⁺(VI) was maximized at B₂O₃/Al₂O₃ = 1. It is considered that the higher coordination of Al³⁺ brings the improvement of the packing and it leads to high refractive index.     

Effect of B2O3 addition on the thermal properties and density of barium phosphate glasses

Variations in glass transition temperature, onset of crystallization, thermal expansion coefficient, density and molar volume with B₂O₃ concentration were studied in a series of xB₂O₃–(100 − x)Ba(PO₃)₂ glasses with 0–10 mol% B₂O₃. DTA analysis and isothermal treatments for powdered glass samples reveal that ⩾7.5 mol% B₂O₃ addition suppresses surface crystallization during softening process. Raman spectroscopy suggests that the properties are related to the glass structure consisting of PO₄ Q² units with diborate and PO₄–BO₄ groups.     

Glass composition dependence of luminescence due to Ge2+ center in germanate glasses

Germanate glasses were prepared by the melt-quenching method using an assembled hot-thermocoupler equipped in a sample chamber of a fluorescence spectrometer, and subsequently their luminescence and excitation spectra were measured. In the GeO₂ glass, luminescence bands due to the Ge²⁺ center appeared at the central wavelengths of 300 and 395 nm, their excitation bands being at 250 and 330 nm, respectively. In the (100 − x)GeO₂ − xM_mO_n glasses, for M_mO_n = B₂O₃ (x ≦ 50), SiO₂ (x ≦ 40), and Al₂O₃ (x ≦ 2), the luminescence intensity and therefore the amount of the Ge²⁺ center increased with increasing the content of M_mO_n, where M^(2n/m)+ ions (B³⁺, Si⁴⁺, and Al³⁺) have lower basicities than a Ge⁴⁺ ion. Contrarily, for M_mO_n = Li₂O (x ≦ 30), Na₂O (x ≦ 20), K₂O (x ≦ 20), CaO (x ≦ 20), SrO (x ≦ 3), BaO (x ≦ 15), ZnO (x ≦ 20), Ga₂O₃ (x ≦ 10), Sb₂O₃ (x ≦ 20), Bi₂O₃ (15 ≦ x ≦ 25), TiO₂ (x ≦ 3), and Nb₂O₅ (x ≦ 10), the luminescence intensity and the amount of the Ge²⁺ center rapidly decreased with increasing the amount of additives and disappeared, where M^(2n/m)+ ions (Li⁺, Na⁺, K⁺, Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Ga³⁺, Sb³⁺, Bi³⁺, Ti⁴⁺, and Nb⁵⁺) have higher basicities than a Ge⁴⁺ ion.     

Improved method for preparation of anhydrous silica by microwave irradiation with spectroscopic characterization and toxicity assay

Amorphous anhydrous silica SiO_{2 (mw)} (99.99%) is successfully synthesized through microwave irradiation technique and time of reaction is reduced up to 1 h. The dehydration phase study of Si–water, Si–OH, Si–O–Si networking, elemental analysis and surface morphology was carried out by FTIR, FTNIR, SEM and EDAX spectroscopic techniques. The broad absorption stretching and bending of Si–OH and H₂O at 3695.38–2832.96 cm^? 1, 1638 cm^? 1 and 1191.20–1017.14 cm^? 1 completely disappeared and appearance of new bands at 946.93 and 797.63 cm^? 1 confirmed the amorphous anhydrous silica with Si–O–Si networking. The SEM images of SiO_{2 (mwc)} described the smooth and fine particle texture and confirmed 99.99% Si–O–Si networking of anhydrous silica. The 99.99% purity was verified by EDAX spectra which exhibited sharp signals only for oxygen and silicon. Toxicity against Monomorium minimum and Tribolium castaneum with 100% mortality and LT₅₀ 91 min and 7.5 h respectively is being reported. It can be used for long storage of grains in the future.     

Structural studies on boroaluminosilicate glasses

Two series of boroaluminosilicate glasses having varying mole ratios of B₂O₃/Na₂O (series 1) and B₂O₃/SiO₂ (series II) were prepared by conventional melt-quench method. Based on ²⁹Si and ¹¹B MAS NMR studies, it has been established that for series I glasses up to 15 mol% B₂O₃ content, Na₂O preferentially interacts with B₂O₃ structural units resulting in the conversion of BO₃ to BO₄ structural units. Above 15 mol% B₂O₃ for series I glasses and for all the investigated compositions of the series II glasses, silicon structural units are unaffected whereas boron exist in both trigonal and tetrahedral configurations. Variation of microhardness values of these glasses as a function of composition has been explained based on the change in the relative concentration of BO₄ and BO₃ structural units. These glasses in the powder form can act as efficient room temperature ion exchangers for metal ions like Cu²⁺. It is seen that the ion exchange does not affect the boron and silicon structural units as revealed by IR studies.     

Flux's influence on the luminescent properties of europium and dysprosium codoped melilite long afterglow phosphor

The europium (Eu^2 +) and dysprosium (Dy^3 +) codoped melilite (Sr₂MgSi₂O₇) long afterglow phosphors are synthesized with H₃BO₃ and Li₂CO₃ fluxes, respectively. The XRD analysis demonstrates similar crystal structure and crystal size of the samples. The SEM presents a better crystallization of samples with flux, other than the one without flux. The excitation and emission spectra of the samples are similar but the decay processes of the afterglow are different. The afterglow properties are enhanced by H₃BO₃ while they are suppressed by Li₂CO₃, due to the different concentrations and depths of traps. The sample without flux has a low trap concentration because of the greater surface. Li⁺ ions reduce the concentration of Sr^2 + vacancies and then the trap depth becomes smaller. B^3 + ions break the potential balance in oxygen vacancies then the attraction to trapped electron is enhanced.     

Structure and properties of the 70Li2S · (30 − x)P2S5 · xP2O5 oxysulfide glasses and glass–ceramics

The 70Li₂S · (30 ? x)P₂S₅ · xP₂O₅ (mol%) oxysulfide glasses were prepared by the melt quenching method. The glasses were prepared in the composition range 0 ≦ x ≦ 10. The glass–ceramics were prepared by heating the glasses over crystallization temperatures. The PO_nS_3?n (n = 1–3) oxysulfide units were produced in the glasses and glass–ceramics by partial substituting P₂O₅ for P₂S₅. In particular, the P₂OS₆^4? unit would be produced by substituting a small amount of P₂O₅ for P₂S₅. The oxygen atoms were incorporated into the Li₇P₃S₁₁ crystal structure because the diffraction peaks of the oxysulfide glass–ceramic shifted to the higher angle side. The glass–ceramic with 3 mol% of P₂O₅ exhibited the highest conductivity of 3.0 × 10^?3 S cm^?1 and the lowest activation energy for conduction of 16 kJ mol^?1. The P₂OS₆^4? dimer units in the oxygen-incorporated Li₇P₃S₁₁ crystal would improve conductive behavior of the Li₂S–P₂S₅ glass–ceramics.