Li2O Glass Research Articles

Lithium Ion‐Conducting Glass–Ceramics of Li1.5Al0.5Ge1.5(PO4)3–xLi2O (x=0.0–0.20) with Good Electrical and Electrochemical Properties

NASICON‐type structured Li1.5Al0.5Ge1.5(PO4)3–xLi2O Li‐ion‐conducting glass–ceramics were successfully prepared from as‐prepared glasses. The differential scanning calorimetry, X‐ray diffraction, nuclear magnetic resonance, and field emission scanning electron microscope results reveal that the excess Li2O is not only incorporated into the crystal lattice of the NASICON‐type structure but also exists as a secondary phase and acts as a nucleating agent to considerably promote the crystallization of the as‐prepared glasses during heat treatment, leading to an improvement in the connection between the glass–ceramic grains and hence a dense microstructure with a uniform grain size. These beneficial effects enhance both the bulk and total ionic conductivities at room temperature, which reach 1.18 × 10−3 and 7.25 × 10−4 S/cm, respectively. In addition, the Li1.5Al0.5Ge1.5(PO4)3–0.05Li2O glass–ceramics display favorable electrochemical stability against lithium metal with an electrochemical window of about 6 V. The high ionic conductivity, good electrochemical stability, and wide electrochemical window of LAGP–0.05LO glass–ceramics suggest that they are promising solid‐state electrolytes for all solid‐state lithium batteries with high power density.

EPR study of V2O5–P2O5–Li2O glass system

$${x\hbox{V}_{2}\hbox{O}_{5}\cdot(100-\hbox{x})[\hbox{P}_{2}\hbox{O}_{5}\cdot\hbox{Li}_{2} \hbox{O}]}$$ glass system, with 0 < x $${\le }$$ 50 mol%, was prepared and investigated by EPR method. For low content of V2O5 all the spectra present a hyperfine structure typical for isolated V4+ ions. With the increasing of V2O5 content, the EPR absorption signal showing hyperfine structure is superposed by a broad line without hyperfine structure characteristic for clustered ions. At high V2O5 content, the vanadium hyperfine structure disappears and only the broad line can be observed in the spectra. Spin Hamiltonian parameters g $$\Vert $$ , g $${\bot}$$ , A $$\Vert $$ , A $${\bot}$$ , dipolar hyperfine coupling parameters, P, and Fermi contact interaction parameters, K, have been calculated.The composition dependence of line widths of the first two absorptions from the parallel band and of the broad line characteristic to the cluster formations was also discussed.

Dielectric properties of P 2O 5–Na 2O–Li 2O glasses containing WO 3, CoO or Fe 2O 3

The aim of this work was to study some polarization mechanisms in phosphate glasses containing different transition metal oxides, performed at radio frequency (100 kHz) and in the microwave region (9 GHz). Cobalt, iron and tungsten oxides were chosen for the present investigation. The results show that the dielectric constant increases linearly with increasing Co concentration, whereas for iron and tungsten ions, the dielectric constant values were found to decrease up to a given concentration and further, increase for higher concentration of W and Fe. This anomaly was observed both at 100 kHz and 9.00 GHz and was attributed to the valence state of the transition metal ions in the glass structure. The dielectric constant is lower in the microwave region, due to structural relaxation mechanisms.

Raman study of xMeO·(100 − x)[P 2O 5·Li 2O] (MeO ⇒ Fe 2O 3 or V 2O 5) glass systems

Glasses from xMeO·(100 − x)[P 2O 5·Li 2O] (MeO ⇒ Fe 2O 3 or V 2O 5) systems, with 0 ≤ x ≤ 50 mol%, were prepared and investigated by Raman spectroscopy. The influence of Fe 2O 3 and V 2O 5 content on the structure of P 2O 5·Li 2O glass matrix was followed. The P 2O 5·Li 2O glass matrix presents three absorption bands characteristic to metaphosphate chain structures. The addition of Fe 2O 3 or V 2O 5 determines the modification of the structure of the studied glasses. The Raman spectra of xFe 2O 3·(100 − x)[P 2O 5·Li 2O] do not present any absorption bands characteristic to Fe 2O 3 but its evolution is dependent on the iron content. The Raman spectra of xV 2O 5·(100 − x)[P 2O 5·Li 2O] present, besides the bands specific for the matrix, some bands assigned to characteristic vibrations of V–O bonds which are evidenced only for high content of V 2O 5. The evolution of the spectra is dependent of V 2O 5 content.

Effect of Ce 3+ on the spectroscopic properties in Er 3+ doped TeO 2–GeO 2–Nb 2O 5–Li 2O glasses

The Ce 3+ ion was introduced into Er 3+ doped TeO 2–GeO 2–Nb 2O 5–Li 2O (TGNL) glass to improve the 1.5 μm fluorescence characteristics. As increasing of Ce 3+ concentration, the lifetime of Er 3+: 4I 11/2 level is shortened form 360 to 225 μs, while the Er 3+: 4I 13/2 level remains unchanged. Accordingly, the upconversion fluorescence (blue, green and red) was quenched. Improved 1.5 μm emission is obtained and the reason is ascribed to the increase of nonradiative rate between the 4I 11/2 and 4I 13/2 level of the Er 3+ ions.

Photostimulated luminescence from BaCl2:Eu2+ nanocrystals in lithium borate glasses following neutron irradiation

A glass-ceramic thermal neutron imaging plate material is reported. The material consists of a neutron sensitive 2B2O3–Li2O glass matrix containing nanocrystallites of the storage phosphor BaCl2:Eu2+. When doped with 0.5mol% Eu2+, the neutron induced photostimulated luminescence (PSL) conversion efficiency of the B10 enriched glass-ceramic is around 60% of that a commercial neutron imaging plate, while the γ sensitivity is an order of magnitude lower than that of the commercial plate. A Eu2+-concentration series shows that the PSL efficiency for x rays is optimized at 0.01mol% Eu2+. Thermoluminescence measurements indicate trap depths in BaCl2:Eu2+ ranging from 0.55to2.7eV.

Upconversion studies in Er 3+ doped TeO 2–M 2O (M=Li, Na and K) binary glasses

The luminescence properties of Er 3+ doped alkali tellurite [ TeO 2–M 2O (M=Li, Na and K)] glasses are investigated. Infrared to visible upconversion emissions are observed at 410, 525, 550 and 658 nm using 797 nm excitation. These bands are assigned to the 2H 9/2 → 4I 15/2, 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2, 4F 9/2 → 4I 15/2 transitions of Er 3+ respectively. Detailed study reveals that the 2H 9/2 → 4I 15/2 transition at 410 nm involves a three-step process while the other transitions involve two-steps. Excitation with 532 nm radiation gives additional bands at 380, 404, 475 and 843 nm wavelengths due to the 4G 11/2 → 4I 15/2, 2P 3/2 → 4I 13/2, 2P 3/2 → 4I 11/2, and 4S 3/2 → 4I 13/2 transitions, respectively, along with the bands observed on NIR excitation. The fluorescence yield is found to be largest for the TeO 2–Na 2O glass. The lifetime of the 4S 3/2 level has been measured for all the three cases and used to explain the upconversion mechanisms. The fluorescence intensity ratio corresponding to the two thermally coupled levels ( 2H 11/2, 4S 3/2) has been used to estimate the temperature of the glass. It is observed that the temperature sensing capacity of TeO 2–Li 2O glass is better than the other two glasses.

Upconversion properties of Er3+/Yb3+co-doped TeO2–Nb2O5–Li2O glasses

The Er3+/Yb3+ co-doped TeO2–Nb2O5–Li2O glass is prepared by conventional melting method and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser diode is observed with the naked eyes. The dependence of luminescence intensity on the ratio of Yb3+/Er3+ is discussed in detail and the relationship between the ratio of green luminescence intensity to red luminescence intensity and the ratio of Yb3+/Er3+ is also studied. The luminescence intensity increases with the ratio of Yb3+/Er3+increasing. The ratio of Yb3+/Er3+ plays a more important role than the concentration of Er3+ in determining the upconversion luminescence intensity. The ratio of green luminescence intensity to red luminescence intensity reaches a maximum when ratio of Yb3+/Er3+ is 3. Thus the glass could be one of the potential candidates for LD pumping solid-state lasers.

The behaviour of a SiO2–Li2O glass ceramic during one-dimensional shock loading

The shock response of a Li2O–SiO2 glass ceramic has been studied by the technique of plate impact. The Hugoniot in terms of impact stress and particle velocity has been measured using embedded stress gauges, showing an increasing complexity of behaviour as impact stress increases. Back surface measurements have revealed the presence of a reload signal, indicating the presence of a moving damage front behind the main shock—the so-called failure wave. This has been confirmed by stress gauges mounted so as to be sensitive to the lateral component of stress. Results show that the shear strength ahead of the failure wave is near elastic in its response. Behind the failure wave, shear strength drops, but is still higher than the equivalent results in silicate glasses, suggesting that this material has superior ballistic resistance.

Comparative study of spectroscopic properties of Er 3+ /Yb 3+ -codoped tellurite glass and fibres under 980nm excitation

A tellurite fibre of TeO2–ZnO–La2O3–Li2O glass codoped with 20000 ppm ytterbium and 5000 ppm erbium was fabricated by the suction casting and rod-in-tube technologies. The absorption spectrum of Er3+/Yb3+ -codoped bulk glass has been measured. From the Judd–Ofelt intensity parameters, the spontaneous emission probability and radiative lifetime τrad of Er3+:4I13/2→4I15/2 transition for the bulk glass have been calculated. The emission fluorescence spectra and lifetimes around 1.5μm and subsequent upconversion fluorescence in the range of 500–700nm were measured in fibres and compared with those in bulk glass. The changes in amplified spontaneous emission with fibre length and pumping power was also measured. It was found that the emission spectrum from erbium in fibres is almost twice as broad as the corresponding spectrum in bulk glass when pumped at 980nm.

FT-EPR spectroscopy in the borate system

80-mol% B2O3 20-mol% Li2O glass has been subjected to γ-irradiation at room temperature and subsequently studied by CW EPR (continuous wave electron paramagnetic resonance), ECHO-fs (field sweep), 4p-ESEEM (electron spin echo envelop modulation spectroscopy), 2D-HYSCORE (hyperfine sublevel correlation) spectroscopy and pulse ENDOR (electron nuclear double resonance) spectroscopies. The variation of the EPR signal with the conditions of measurements suggests that several centers contribute to the signal. The Aiso-couplings of the next neighbor have been determined by these methods. One may suggest on this ground the existence of the tetraborate, diborate and boron network non-bridging oxygen (BN-nbo) structures, though this preliminary effort needs supplementary investigational work to be convinced about it.

Study of electron paramagnetic resonance, optical transmission and dc conductivity of vanadyl doped Bi 2O 3·B 2O 3·Li 2O glasses

Glasses with composition xBi 2O 3·(70− x)B 2O 3·30Li 2O containing 2 mol% V 2O 5 have been prepared over the range 0≤ x≤20 (in mol%). The electron paramagnetic resonance (EPR) spectra of VO 2+ ions of these glasses have been recorded in the X-band (≈9.13 GHz) at room temperature. Spin Hamiltonian parameters (SHP), g ||, g ⊥, A ||, A ⊥, dipolar hyperfine coupling parameter, P, and Fermi contact interaction parameter, K, have been calculated. The molecular orbital coefficients, α 2 and γ 2, have been calculated by recording the optical transmission spectra in the wavelength range of 500–850 nm. It has been observed that the octahedral symmetry around V 4+ ion is improved, and the 3d xy orbit of the unpaired electron of the vanadium ion expands with increase in Bi 2O 3:B 2O 3 ratio. Values of the theoretical optical basicity, Λ th, have also been reported. The dc conductivity increases with an increase in temperature. The dc conductivity variation with Bi 2O 3 content shows mixed glass-former effect at x=8 mol%. For x=10 mol%, the conductivity decreases with increase in Bi 2O 3 content because of the decrease in the mobility and the number of Li + ions available for the conduction.

EPR and magnetic susceptibility studies on polaron dynamics in V2O5-, MoO3- and CuO-containing glasses

Abstract EPR lineshapes studies on 0.7V2O5–0.3P2O5 (S1), 0.8MoO3–0.2B2O3 (S2), 0.5MoO3–0.2Sb2O3–0.3K2O (S3), and 0.05CuO–0.7B2O3–0.25Li2O (S4) glasses were performed at various temperatures. The trends in g-values of g|| 300 K are found to be 0.001 eV for the glasses S3 and S4.

HYSCORE spectroscopy in the borate glasses

Glasses of the composition xB 2O 3–Li 2O, with x=1, 2, 3, 4 and 5 were exposed to 60Co γ-irradiation and measured with hyperfine sublevel correlation (HYSCORE) spectroscopy. The HYSCORE spectra were explained with the assistance of a simulation procedure developed in-house in order to extract important parameters describing the Hamiltonian of the second boron neighbor of the paramagnetic state. HYSCORE spectroscopy in the xB 2O 3–Li 2O glasses revealed A iso couplings, the strength of which varies with x. In few cases, structural models could be proposed which may account for the HYSCORE spectra. The HYSCORE spectrum of the 4B 2O 3–Li 2O glass exhibits cross peaks in both (+, +) and (+, −) quadrants indicating the presence of a complex structure.

Spectral analysis of Ho3+: TeO2–B2O3–Li2O glass

A highly transparent and little yellow-coloured Ho3+ doped TeO2–B2O3–Li2O glass was prepared in order to study its optical properties from the measured UV–VIS–NIR absorption, emission and up-conversion emission spectra. We observed a prominent and bright red colour when this optical glass was brought under a UV lamp. The recorded up-conversion emissions revealed a strong green colour along with blue and violet colours upon excitation with λexc=643 nm, and the mechanism was explained by an energy level diagram as a three photon absorption process.

Electron Paramagnetic Resonance Study of Positive-Hole Pairs on Oxide Ions in Lithium Bismuthate Glass

Abstract The electron paramagnetic resonance signals attributed to the triplet state of the positive-hole pairs on oxide ions are observed in (100−x) Bi2O3·x Li2O glass (x = 25, 30, 35 mol%). So far as we know, this is the first experimental observation of the triplet oxygen hole center in oxide glasses.

Absorption and photoluminescence spectra of Sm 3+:TeO 2–B 2O 3–P 2O 5–Li 2O glass

This short communication reports the optical properties of Sm 3+-doped 65TeO 2 + 12B 2O 3 + 12P 2O 5 + 10Li 2O glass based on the spectrophotometric profiles of absorption (300 K) and fluorescence (300 and 10 K) spectra.

Computer simulations of electron paramagnetic resonance spectra of P 2O 5Li 2WO 4Li 2O glasses

P 2O 5Li 2WO 4Li 2O glasses have been synthesized and studied over a wide range of compositions. The glasses were characterized mainly by thermodifferential analysis and electron paramagnetic resonance (EPR). The EPR spectra are characterized by the presence of two signals with very different intensities, associated with the W v (major signal) and Mo v (minor signal) paramagnetic centres. The signals have been satisfactorily reproduced by computer simulation, assuming anisotropy in the g values as well as the hyperfine parameters and linewidths. EPR parameters have been extracted and indicate metallic ions located in environments close to square pyramidal.

Optical properties of vanadate glasses in relation to composition and structure

Infra-red spectra of binary V 2O 5P 2O 5 and ternary V 2O 5P 2O 5Li 2O glasses were studied and compared with the infra-red spectra of the corresponding crystalline reference materials. The results indicate that the fundamental vibration frequency of the VO bond occurred at 1005–1020 cm −1, together with the characteristic bands due to PO units. The probable structure of vanadate glasses was considered together with the effect of lithia on the absorption bands.

NMR Studies of Diffusion in Glassy and Crystalline Lithium Borates

The 7Li NMR spectra from several lithium borate glasses have been examined as a function of temperature and found to narrow abruptly with increasing temperature in the range of temperatures from 250° to 475°K. The observed narrowing is a manifestation of the phenomenon of motional narrowing, and is attributed to diffusion of the lithium ions in the glasses. Activation energies for this diffusion, as deduced from the temperature dependence of the 7Li NMR linewidths, range from 0.22 eV in a glass containing 28.6 molar % Li2O to 0.12 eV in a 60 molar % Li2O glass. The 7B NMR lines from these glasses are reduced somewhat with increasing temperature because of the removal of the lithium-boron dipolar interaction with the onset of the lithium diffusion. The linewidths of the 7Li spectra from the crystalline lithium borates also decrease with increasing temperatures and the activation energies obtained from their narrowing rates range from 0.14 eV in the Li2O·4B2O3 compound to 0.43 eV in the 3Li2O·2B2O3; compound. It has been concluded that the ionic movement responsible for the narrowing of the resonance spectra is motion within limited regions, rather than the movement over long distances necessary for electrical conductivity.