Lithium Phosphate Glasses Research Articles

Thermal, mechanical and electrical properties of lithium phosphate glasses doped with copper oxide

Lithium phosphate glasses with the basic composition ( $${\hbox {P}}_{2} {\hbox {O}}_{5}$$ 50 and $${\hbox {Li}}_{2} \hbox {O}$$ 50 mol%) series by the addition of copper oxide (0, 10, 15 and 20 g/100 g) were prepared by a melt quenching technique. Fourier-transform infrared (FTIR) absorption spectra and X-ray diffraction (XRD) analysis were used to characterize the glass samples. Thermal expansion and mass density were also measured. The different mechanical properties of the prepared glasses were measured by an ultrasonic non-destructive technique. Additionally, both frequency and temperature dependence of alternating-current conductivity were measured in the frequency range of 40 Hz–1 MHz and the temperature range of 308–488 K. Moreover, direct current conductivity was also measured for the same temperature range. FTIR measurements confirm the appearance of the bands of phosphate groups and the assumption of bonds formed between Cu and P. XRD spectra approve the amorphous nature of the studied glasses. Thermal expansion and mass density of the prepared samples show an increase in values by increasing the CuO content. The mechanical properties of the studied glasses (hardness ( $$H_{\mathrm{v}}$$ ), Young’s modulus (E), elastic modulus (L), bulk modulus (K), shear modulus (G) and Poisson’s ratio ( $$\nu $$ )) were positively affected by the CuO content, reflecting a better packed structure. Furthermore, the electrical conductivity values of the prepared glasses are identified to increase with an increase in both temperature and CuO content. Such trends agree with the data obtained by thermal expansion and FTIR. The progressive addition of CuO is assumed to improve thermal, mechanical and electrical properties of the prepared lithium phosphate glasses.

Characterization of Cr3+ doped zinc lead lithium phosphate glasses

Cr3+ metal ion doped Zinc-Lead-Lithium-Phosphate glass samples are made by melt quenching technique, by varying 0.2% mol (20-x) Li2CO3−x Cr2O3 in glass mixture composition. To identify basic structural units in these glasses, to investigate structural changes with the change in glass composition and to relate structural changes with the difference in properties of glasses, the samples subjected to spectral studies of XRD, UV–vis, EPR and FTIR. The physical properties of the glass samples like average molecular weight, Cr3+ ion concentration, density, refractive index etc, were calculated. Spin–Hamiltonian parameters are evaluated from EPR spectra which exhibit two resonance intense signals representing coupled pair and free state of Cr3+ ions. The breakage of Phosphorous—Oxygen—Phosphorous (P–O–P) link and the development of cross ionic bonding among the chains of phosphate are identified in FTIR spectra. From optical absorption spectra, crystal field parameters and optical band gap values have been calculated. The optical band gap value of the prepared phosphate glasses is found to lie in the range 1.60–1.63 eV, which fined immediate applications in the fabrication of ultra high speed Integrated circuits, IR photon detectors and thin films.

Influence of Er3+ ions on the physical, structural, optical, and thermal properties of ZnO–Li2O–P2O5 glasses

Er3+ doped zinc lithium phosphate glass samples were synthesized by the very simple melt quenching method. The obtained X-ray diffraction patterns specify that the prepared glass samples exhibit glassy nature. The physical properties like packing density, molar volume, density, oxygen packing density, interionic distance, field strength, rare earth ion concentration, and polaron radius were calculated using appropriate formulae. DTA curve was analysed to evaluate the crystallization temperature, melting temperature, and glass transition temperature and hence study the thermal properties. Fourier transform infrared spectrum was recorded to examine the functional groups in the glass and study the structural characteristics of the glass. It showed the presence of symmetrical and asymmetrical stretching vibration modes of P–O–P linkages, bending modes of P–O in PO4, bending and stretching vibrations of OH groups and P–O–H water absorbance in the glasses. The absorption spectra of the prepared glasses in the UV–visible region (wavelength 200–1100 nm) were taken to study the optical properties of the glasses. The urbach energy and optical energy bandgap values are determined using Davis–Mott method. The refractive index of all the prepared glass samples is also measured and these values are used to determine the corresponding molar refraction, the molecular polarizability of oxide ions, dielectric constant, reflection loss, metallization criterion, electronic polarizability of the oxide ions, interaction parameter, electronegativity, optical basicity, and electric susceptibility of all the glass samples using appropriate formulae.

Thermal and Structural Properties of Zinc Lithium Phosphate Glasses with Holmium Ions (Ho3+)

Holmium-doped zinc lithium phosphate glasses with formula xHo2O3-(15-x) Li2O-45ZnO-40P2O5 (where x=0, 0.1, 0.3 and 0.5 mol%) are synthesized by conventional melt quenching method. X-ray diffraction results confirmed that the prepared glass samples exhibit amorphous nature. Using DTA curves, the glass transition, crystallization and melting temperatures-Tg, Tc, and Tm respectively are determined and the thermal properties of all the prepared samples are studied. Fourier transform Infrared spectrum (FTIR) was used to examine the structural properties of the glasses. It showed the presence of stretching vibration modes of P-O-P, bending modes of P-O in PO4, stretching and bending vibrations of OH groups.

Physical, optical and morphological studies of V2O5 doped zinc lead lithium phosphate (ZnPbLiP) glasses

Abstract Vanadium ion doped zinc lead lithium phosphate glass samples are prepared by melt quench method. X-ray diffraction studies confirmed the amorphous nature of all the prepared glasses. The density and refractive index values of these glasses are evaluated using the Archimedes method and Abbe’s refractometer respectively. The values of density found to be in between 3.6363 and 3.6666 g/cm3. The refractive index values are observed in the range 1.5605–1.5620. An increasing trend has been observed in density and refractive index from the simultaneous variation of Li2CO3 and V2O5 in the host matrix. Optical absorption spectra of these samples exhibited two absorption bands at 548 and 738 nm which indicate the characteristic absorption peaks of V4+ ions. The optical basicity values of the studied glasses V1–V5 are identified to slightly vary from 0.6736 to 0.6718, which represents electron donor ability of oxide ions to the cations. The knowledge on optical basicity finds immediate applications in the design of the novel optical functional materials like polarizers, detectors and modulators with higher optical performance. The morphological variations have been observed in the studied glasses upon doping of V2O5 by using Scanning Electron Microscopy.

On the Electrochemistry of Lipon Breakdown

Solid electrolytes are considered a necessary step for Li-ion ions to surpass the practical limit of 800Wh/L. Next to safety aspects, solid-state electrolytes could enable more compact batteries thus increasing their volumetric storage capacity. A main driver, however, is the potential for solid-electrolytes to increase the electrochemical window to accommodate high voltage positive electrodes (5V cathodes) and stability against metallic lithium as negative electrode. As such, solid-state batteries could enable high energy density through increased cell voltage. Numerous Li-ion conducting solids are known today, however most do not have the broad electrochemical window and stability against lithium yet. Nitrogen doped lithium phosphate glass or LiPON is a well known solid electrolyte material attributed with excellent electrochemical stability above 5V and stable against metallic lithium [1]. However, due to its limited ionic conductivity (~10-6 S/cm) it is only applicable in thin-film batteries for use for medical implants and various sensor systems. It has also been evaluated as solid-electrolyte coatings on electrode particles as buffer layer between active material and the bulk electrolyte. In a thin-film stack, it is an ideal model system for electrochemical study. In this paper, we report on the electrochemistry of RF-sputtered LiPON thin films and studied the out plating of lithium until break down. The LiPON thin-films had ionic conductivities ranging between 1x10-7 and 1x10-6 S/cm [2]. The decomposition potential was calculated from basic thermodynamic quantities and was linked to current-voltage (I-V) measurements with great consistency. The reported I-V measurements were conducted on metal-electrolyte-metal or MEM structures. The decomposition of LiPON was shown to occur at a potential of 4.8 V and proceeds in a diffusion limited way. It could be shown that LiPON breakdown is rather determined by the time needed for the decomposition reactions to complete, rather than being solely driven by the electric field. From the diffusion limited Li-ion current, the Li+ diffusion coefficient was extracted and found to be 2x10-11 cm2/s. This value is in excellent agreement with literature reports [3]. Ultimately hard breakdown was shown by TOF-SIMS imaging experiments and occurs through the formation of metallic lithium filaments. In the present work, we have for the first time formulated a breakdown mechanism for LiPON layers based on experimental measurements and thermodynamic considerations. The presented work provides a detailed evaluation of a solid electrolyte's breakdown and stability using I-V measurements. As such these measurements allow determination of ion transport phenomena as well as of the electrochemical stability window. It can also provide insight in the breakdown mechanism of RRAM devices.

Electrical and dielectric analysis of lithium chloride mixed sodium and lithium phosphate glasses

AbstractGlasses with molar composition 2xLiCl–(40−x)Na2O–(40−x)P2O5–20Li2O, where 0 ≤ 2x≤7 (mol%), were prepared by the melt‐quenching method. The synthesized glasses were characterized by X‐ray diffraction, which confirmed their amorphous nature. The glass transition temperature and crystallization temperature of the samples were determined by differential thermal analysis. The density of the samples was measure using Archimedes principle, and the structural analysis was further investigated using infrared and Raman spectroscopy. The dc conductivity of the samples was investigated, along with their dielectric properties using impedance spectroscopy, in the frequency range 100 Hz to 1 MHz, which showed a maximum of conductivity for the sample with 7 mol% of LiCl. The results were correlated to the increased number of lithium ions and to the chloride ions which can either form P–Cl bonds or occupy the interstitial sites of the glass network.

A comparative property investigation of lithium phosphate glass melted in microwave and conventional heating

The present study addresses the application of microwave (MW) energy for melting lithium phosphate glass. A comparative analysis of the properties is presented with glasses melted in conventional resistance heating adopting standard methods of characterization. The density of the glass was found less in MW heating. The glass transition temperature was recorded as 3–10\({^{\circ }}\hbox {C}\) lower in MW prepared glass than in conventional glass. Micro-hardness is found to be improved in case of MW heating. Maximum forward power was recorded less than 2 kW with an average power \(\sim \)1 kW during melting of 40 g glass in MW furnace. MW forward and reflected power measured during melting in the MW cavity was elaborated. Total melting time was within 2 h 30 min in MW heating, whereas it was 6–7 h in resistive heating. Total power consumed was \(\sim \)5 kWh in MW heating and \(\sim \)14 kWh in resistance heating.

Electrical conductivity and dielectric properties of MgO doped lithium phosphate glasses

The electrical and dielectrical properties of Li2O-P2O5-Al2O3 doped with MgO glasses were measured using complex impedance spectroscopy. IR study reveals the influence of gradual increase in MgO content on the glass structure. The Nyquist diagrams were investigated in terms of equivalent circuits due to resistors and constant phase elements (CPE). Constant-phase elements (CPE) were used in equivalent electrical circuits for the fitting of experimental impedance data. Complex impedance analysis showed the behavior of a dielectric relaxation non-Debye type. The ac conductivity increases with temperature following the Arrhenius law, with single apparent activation energy for conduction process. The variation of conductivity and high temperature activation energy with composition revealed the possibility of ionic contribution to the conductivity and a transition from predominantly polaronic conductive regime to ionic conductive regime around 1.5mol% of MgO in lithium phosphate glasses. The frequency dependence of the electric conductivity follows a simple power law behavior, according to relation σac(ω)=σ(0)+Aωs, where s<1. It was evident that the electrical transport process in the system was due to the hopping mechanism. The frequency and temperature dependence of the electrical modulus as well as dielectric loss parameters have exhibited a relaxation character.

Improvement of thermal and optical properties of lithium phosphate glasses by adding MgO

Collective characterizations of prepared lithium phosphate glass together with samples containing increasing added MgO contents (0–2 mol%) were carried out by differential thermal analysis (DTA), spectroscopic ellipsometry (SE) and photoluminescence (PL) measurements. From the DTA profile, the glass transition temperature T g and crystallization onset temperature T x are estimated. The thermal stability factor was higher than 100 °C suggesting that this glass exhibits a good thermal stability and consequently is suitable to be a potential candidate for fiber drawing. Furthermore, the variation of the ΔT as function of MgO contents has a minimum at 1 mol% of MgO. The refractive index and extinction coefficient data were obtained by analyzing the experimental spectra of tanΨ and cosΔ measured by SE. The complex dielectric functions (e = e 1 + ιe 2) of the samples were estimated from regression analysis. Some of the optical absorption parameters, such as high-frequency dielectric constant, e ∞, the average values of oscillator strength, S o, wavelength of single oscillator, λ o, plasma frequency, ωp, and relaxation time, τ, have been evaluated. The PL spectra of the MgO-doped glass under 325-nm excitation wavelength were studied. The dependence of PL spectra on doping concentration shows a quenching of the PL intensity for MgO concentration above 1 mol%. The variations of the photoluminescence intensity, thermal stability refractive index and optical constants gave an indication to use the prepared glasses for design of novel functional optical materials with higher optical performance.

Plasma - Assisted ALD of Lipo(N) for Solid State Batteries

Present-day planar thin-film solid state Li-ion batteries provide an excellent power density and improved safety over their liquid counterparts. However, their energy density remains typically low. For this reason the transition to a 3D thin film battery is presently being explored. This preserves the extreme power characteristics associated with the usage of thin films while increasing the amount of active material and therefore the energy density. Key to the realization of such battery is the possibility to coat these large surface area structures in a conformal and defect free way1. This aspect is especially critical for the solid electrolyte which provides electronic insulation between the two electrodes. Nitrogen-doped lithium phosphate glass or LiPON, is the solid state electrolytes of choice for planar thin-film batteries. This is attributed to its good electronic insulating properties, its wide electrochemical window (0 - 5.5V vs Li+/Li) and reasonable ionic conductivity (~10-6 S/cm). The ionic resistance of the LiPON is still below 100 Ω.cm2 when the film thickness is kept below 1 μm. It was shown recently that LiPON layers can provide electronic insulation down to 15 nm.2 Atomic layer deposition (ALD), which is a vapor based technique with sequential and self-limiting reactions, is known to provide excellent conformality and thickness control (down to sub-nm level). Hence, it is ideally suited for the deposition of the solid electrolyte in thin film battery applications. Recently both thermal and plasma assisted ALD of LiPON was shown3,4. In this work we report the deposition of Li3PO4 and LixPOyNz using LiOtBu and TMPO as precursors and H2O (or O2 plasma) and N2 plasma as reactants. The effect of these different processing conditions on the stoichiometry is studied by a combination of Elastic Recoil Detection (ERD) and X-ray Photoelectron Spectroscopy (XPS). As expected, nitrogen is incorporated in the Li3PO4 layers by sequentially exposing the layers to a N2plasma. For the first time the electrical and electrochemical properties were investigated for a range of different material compositions and thicknesses in detail. Large varieties in ionic conducitivity (between 10-14 – 10-7 S/cm) and activation energy were measured by impedance spectroscopy for the different processing conditions. DC-polarization measurements showed good electronic insulating properties for films below 50 nm (ρ ~ 1015 Ω.cm). Such thin films lead to a minimal ionic resistance (on the order of 1.5 Ω.cm2for the thinnest layer), which can facilitate extreme charging and discharging kinetics. Finally, the deposition of these layers was tested in high aspect ratio pillar arrays and in Li-ion half cells comprising TiO2/LiPO(N) and LiMn2O4/LiPO(N). The layers fabricated here can serve as electrolyte in the all solid state 3D batteries. However, they also hold potential as buffer layer to stabilize electrodes in a classical wet battery. Vereecken et al., ECS transactions, 58, 111-118, 2013Put et al., ACS Applied materials & interfaces, 8, 7060–7069, 2016Kozen et al., Chemistry of materials, 27, 5324-5331, 2015Nisula et al., Chemistry of materials, 27, 6987–6993, 2015 Figure Caption: Figure 1: Complex plane plot of a Li3PO4 layer showing the characteristic semi-circle associated with Li-ion conductivity through the layer. The inset shows the conformal coating of a high aspect-ratio pillar array. Figure 1

Lithium diffusion coefficient in amorphous lithium phosphate thin films measured by secondary ion mass spectroscopy with isotope exchange methods

Lithium diffusion coefficients in amorphous lithium phosphate (a-Li3PO4) thin films were determined by secondary ion mass spectroscopy (SIMS), using 7Li and 6Li stable isotopes. The diffusion couples were prepared by an ion-exchange method using liquid electrolyte and a mask method based on thin-film deposition. The tracer diffusion coefficient, DLi⁎, was evaluated by analyzing the isotope profiles obtained by SIMS in the temperature range of 25–160°C. The diffusion coefficient of a-Li3PO4 was 6.0×10−13cm2/s at 25°C, while the activation energy was 0.58eV, as measured for the samples prepared by using the ion-exchange method. The conductivity diffusion coefficient, Dσ, was calculated from the thin film ionic conductivity, which was determined by impedance spectroscopy. The correlation factor, HR, was 0.55±0.20 in the measured temperature range, which indicated the cooperative motion of lithium ions in lithium phosphate glasses.

Electrochemical performance as cathode of lithium iron silicate, borate and phosphate glasses with different Fe2 + fractions

Lithium iron silicate glasses with different fractions of Fe2+ ions of 40Li2O–10Fe2O3–50SiO2 (mol%) are prepared by conventional melt-quenching method and reducing heat treatment technique, and their electrochemical properties as cathode materials for Li+ ion secondary batteries (LIBs: lithium ion batteries) are examined. It is demonstrated for the first time that Li2O–Fe2O3–SiO2 glasses work as cathode in LIBs, e.g., the discharge capacity at 100/C in the first cycle is 54.6mAhg−1. The heat treatment at 350°C in 5% H2/Ar induces not only the increase in the fraction of Fe2+ ions but also the increase in the packing density and the decrease in the electrical conductivity. It is clarified that the discharge capacity of the glasses is largely improved due to the increase in the fraction of Fe2+ ions. The data on thermal, physical, and discharge properties obtained in 40Li2O–10Fe2O3–50SiO2 glasses are compared with those in borate and phosphate glasses of 40Li2O–10Fe2O3–50(B2O3, P2O5).

Lithium–germanium–phosphate glassceramic electrolytes: correlation between the nanocrystallization and electrical studies

Investigations on the microstructural and electrical properties of a glassceramic system: (100 − x) [0.4Li2O − 0.1GeO2 − 0.6P2O5] + x [20 h ball milled Ga2O3] (0 ≤ x ≤ 10 mol%, in the regular steps of 2 mol%) via high-energy ball milling technique are reported. XRD spectra of LGePG glassceramic samples were identified major crystalline phases such as Li3Ge2(PO4)3 (NASICON-type phase), Ga2Li3(PO3)7 and GeO2 from the major diffraction peaks. Bulk conductivity of all these samples was measured for the powder-compressed pellets by ac impedance method. The correlation of log(σ) and M″ peaks suggests the presence of single conduction mechanism in the LGePG glassceramic samples. The results are discussed in the light of degree of crystallization of lithium phosphate glass network.

Structural Features of LiPON Glasses Determined by 1D and 2D 31P MAS NMR

The relationships between structure and electrical properties of nitrided lithium phosphate glasses (LiPON) used as electrolytes for lithium batteries are key issues for better understanding and design of these materials. For the first time, the effect of nitrogen introduction in the structure of lithium phosphorus oxynitride glasses, formulated over a wide range of composition 38–55 mol.% of Li2O, has been studied through 31P 1D/2D MAS NMR experiments. Information obtained from 2D 31P/31P correlation maps has been used to deconvolute the 1D 31P NMR spectra and allowed establishing the percentage of oxide phosphate groups (PO4) and phosphorus species with nitrogen (P(O,N)4) as well as the connectivity scheme of the phosphate network. Finally, it has been demonstrated that the lithium content affects the structural changes induced by the introduction of nitrogen. In particular, the lower the lithium content is, the lower the total percentage of nitrided P(O,N)4 species is.

Effect of fluorine and nitrogen on the chemical durability of lithium phosphate glasses

The dissolution of glasses belonging to the systems of composition xLi2O·(100−x)P2O5 (x=38–55mol%) and (55−x/2)Li2O·xLiF·(45−x/2)P2O5 (x=10–30mol%), with and without nitrogen, has been studied through immersion of the samples in water at 95°C using a Soxhlet extractor. In this work, a wide range of compositions prepared by melting has allowed a detailed study of the effect of nitrogen and fluorine in the chemical properties of glasses with variable lithium contents. In lithium phosphorus oxynitride glasses, it was demonstrated that low lithium and high nitrogen contents improve the chemical durability. However, there is a maximum of nitrogen percentage from which the durability is not further improved. In lithium phosphorus fluoro-oxynitride glasses, fluorine introduction leads to a deterioration of the phosphate glasses; however, the introduction of nitrogen in these glasses increases significantly the chemical durability. The structural changes obtained by NMR and XPS are used to explain the effect of lithium, fluorine and nitrogen on the chemical properties. In general, the decrease of non-bridging oxygens and the increase percentage of phosphorus groups with nitrogen increase the chemical resistance.

Modeling, Structural, and Spectroscopic Studies of Cobalt-doped Lithium Phosphate Glasses and Effect of Gamma Irradiation

Undoped and cobalt oxide-doped lithium phosphate glasses were prepared by normal melt annealing technique. The structure and optical properties were investigated in order to understand the spectroscopic properties and state of cobalt in this host glass. The glass samples were characterized by combined UV-Visible and Fourier transform infrared absorption spectroscopic techniques. Ultraviolet and visible spectroscopy is used to determine the optical absorption spectra of the base undoped glass and that due to the cobalt ions in this host glass. Spectroscopic investigations were approved using the density functional theory calculations, which were employed to interpret both theoretical and experimental IR data of this glass system and to identify the main building structural groups present in these glasses. Experimental results indicate that divalent cobalt ions occupy more than one coordination state, namely, the octahedral and tetrahedral forms. The changes in the UV-Vis and infrared spectral data are discussed in relation to the change in the state of cobalt ions with glass composition or dopant concentration or structural evolution caused by the changes in glass constituents.

Nitrogen and fluorine anionic substitution in lithium phosphate glasses

Abstract Phosphate based glasses containing simultaneously fluorine and nitrogen in significant amounts have been prepared according to a new synthesis route described in this paper. The results obtained on glass series based on a 55Li2O·45P2O5 composition (mol %) allow, for the first time, the investigation of the effect of fluorine introduction on lithium phosphate and lithium phosphorous oxynitride glasses. New structural features, including the presence of an unreported fluorine site and a change in the Q2 groups/fluorinated species ratio which depends on the lithium fluoride content, were derived from 1D 19F and 31P solid state NMR essays. Distinction between pure phosphate and fluorinated phosphate groups was established using the 2D 31P{19F} CP-HETCOR experiments. The evolution of the glass structure was studied as a function of the lithium fluoride content. The study of the properties of these glasses showed an increase of the ionic conductivity and a decrease of the glass transition temperature due to the phosphate network depolymerisation when lithium fluoride is introduced in the formulation.

Gamma rays interaction with copper doped lithium phosphate glasses

Undoped and copper-doped lithium phosphate glasses were prepared. CuO-doped glasses possess characteristic greenish color which deepens with the increase of CuO content. Experimental optical absorption spectra of the undoped lithium phosphate glasses reveal strong ultraviolet absorption bands and no visible bands are observed. These strong UV bands are assumed to originate from unavoidable trace iron ions contamination within the chemicals used for the preparation of the glass. The optical absorption spectra of the CuO-doped phosphate glasses reveal the same UV absorption as observed in the undoped samples beside an extra broad visible absorption band which splits to some component peaks. Such visible spectra are related to the presence of divalent copper (Cu2+) ions in distorted octahedral coordination. Gamma irradiation of the undoped sample produces induced defects generated through the liberation of pairs of electrons and positive holes. CuO-doped glasses show some shielding behavior towards successive gamma irradiation especially at high CuO contents. FTIR absorption spectra of the studied glasses indicate the appearance of characteristic vibrational bands due to phosphate groups. Gamma irradiation causes minor effects on the FTIR spectra, but the bands due to water molecules are strongly affected by gamma irradiation because of loose bonding within the glass network.

UV-visible and infrared absorption spectra of Bi2O3 in lithium phosphate glasses and effect of gamma irradiation

Ultraviolet and visible absorption spectra of prepared undoped lithium phosphate glass and samples of the same nominal composition with additional Bi2O3 contents were measured before and after being subjected to gamma doses of 3 and 6 Mrad. The base undoped lithium phosphate glass exhibits strong charge transfer ultraviolet absorption bands, which are related to unavoidable presence of trace iron impurities within the raw materials for the preparation of this glass. Bi2O3-containing glasses show the extension of UV absorption beside the resolution of visible bands at 400, 450, and 700 nm with the increase of Bi2O3 content due the sharing of absorption of Bi3+ ions. Gamma irradiation of the base glass reveals extended induced bands; the UV bands are related to the conversion of some Fe2+ to Fe3+ through photochemical reactions during the irradiation process. The visible induced bands are related to the formation of positive hole centers from the host phosphate glass. Glasses containing Bi2O3 are observed to show some shielding behavior, which is attributed to the presence of heavy weight and large atomic number of Bi3+ ions. Infrared absorption spectral measurements of the base lithium phosphate glass show characteristic vibrational modes which are related to specific phosphate groups. The addition of Bi2O3 in measurable percent produces additional vibrational bands due to the introduction of Bi–O groups such as BiO3 and BiO6.