Decrease In Molar Volume Research Articles

Stability of Fe5O6 and its relation to other Fe-Mg-oxides at high pressures and temperatures

Abstract The stability of Fe5O6 has been experimentally determined under pressure-temperature conditions relevant for the Earth’s deeper upper mantle down to the upper portion of the lower mantle (to 28 GPa). In addition, we investigated the incorporation of Mg into Fe5O6 and its systematics, which allows us to discuss the relevance of this phase for the mantle. Experiments were performed from 8–28 GPa and 900–1600 °C. Additional oxide phases may appear if the bulk composition does not maintain the Fe32+Fe23+O6 stoichiometry during the experiment, including coexisting Fe4O5 or Fe9O11. Unfortunately, the similarities in Raman spectra between several high-pressure Fe-oxide phases make this method unsuitable for distinguishing which phase is present in a given sample. The stability field for Fe5O6 extends from ~9 to at least 28 GPa but is truncated at lower temperatures by the assemblage Fe4O5 + wüstite. Refined thermodynamic properties for Fe5O6 are presented. The range of redox stability of Fe5O6 appears to be more limited than that of Fe4O5. Solid solution along the Fe5O6-Mg3Fe2O6 binary is quite limited, reaching a maximum Mg content of ~0.82 cations per formula unit (i.e., XMg3Fe2O6 ≈ 0.27) at 1400 °C and 10 GPa. The observed sharp decrease in molar volume of the O6-phase with Mg content could be a possible explanation for the limited range of solid solution. A phase diagram has been constructed for a composition of approximately Mg0.5Fe2.52+Fe23+O6 stoichiometry. This small amount of Mg causes a significant change in the relations between the O6-structured phase and the assemblage O5-structured phase + (Mg,Fe)O. Several experiments were performed to test whether the O6-phase can coexist with mantle silicates like wadsleyite and ringwoodite. In all cases, the run products contained (Mg,Fe)2Fe2O5 rather than the O6-phase, further underlining the limited ability of Fe5O6 to accommodate enough Mg to be stable in a mantle assemblage. The large stability field of Fe5O6 implies that this phase could likely occur in locally Fe-rich environments, like those sampled by some “deep” diamonds. However, the limited solubility of Mg in the O6-phase leads us to conclude that the O5-phase should be of much more relevance as an accessory phase in a peridotitic mantle assemblage.

Study of the Effect of Chlorides and Bromides on Critical Micelle Concentration and Partial Molar Volume of Quaternary Ammonium Salt

The critical micelle concentration (CMC) of the selected surfactant belonging to quaternary ammonium salts with chemical designation N,N-dimethyl-N-(3-((1R,5S)-1,8,8-trimethyl-2,4-dioxo-3-azabicyclo[3.2.1]octane-3yl)propyl)hexadecane-1-amine bromide was determined. Simultaneously, the effect of the addition of various concentrations of NaCl, KCl, NaBr, and KBr salts on the CMC value of the substance was observed and compared with those obtained in an aqueous solution at T = 296,15 K. Based on the results obtained, it was concluded that NaCl and KCl salts decreased the critical micelle concentration, while NaBr and KBr salts did not support micellization and CMC values therefore increased. In the case of solutions of a substance in the salt environment, when compared to the substance's solution in distilled water, a decrease in partial molar volume was observed. From the concentration density dependencies of the substance, an ionization degree of α was determined. Finally, the molar Gibbs energy ∆G° was also calculated and found negative for all salt solutions, while increase with their increasing concentration.

Effect of the manganese-cobalt substitution on the micro-hardness and thermal properties of zinc phosphate glasses

Metaphosphate glasses belonging to the 10ZnO-(40-x)CoO-xMnO2-50P2O5 system, with 0 ≤ x ≤ 40 mol%, have been synthesized by the melt-quenching technique. The obtained glasses are colored. Some physical parameters such as density, molar volume, and packing oxygen density are determined. It is observed that all these parameters are composition-dependent. The density and molar volume decrease and increase as MnO2 content increases, respectively. Thermal properties were studied with a differential thermal analysis. The glass transition temperature (Tg), crystallization temperature (Tc), and the thermal stability (ΔT) of each glass are evaluated. It is found that glass transition temperature (Tg) and the ionocovalent crosslink density (ICd) decrease with increasing the Mn/Co ratio. It is worth noting that the highest value the thermal stability (ΔT = 192 °C) is obtained for the glass containing high-MnO2 content (x = 30 mol %). The effect of MnO2 on the rigidity of the glasses is also studied by the determination of the micro-hardness (Hv) values. It is observed that this parameter increases with increasing of MnO2 content. This trend is explained according to the bond strength.

Structural, dielectric and optical properties of Ta2O5-Bi2O3-P2O5phosphate glasses

Glasses with the formula 5Ta2O5-xBi2O3-(95-x)P2O5for 10 ≤x≤ 20 mol% were prepared using the standard melt-quench method and identified using X-ray diffraction, Differential Scattering Calorimetry, and Infrared spectroscopy. Furthermore, the dielectric and optical characteristics were determined. The glass transition temperature (Tg) increases linearly with bismuth oxide content, from 524 °C forx= 10 mol% to 582 °C forx= 20 mol%. When the amount of Bi2O3in the system increases, the density rises and the molar volume (VM) decreases. The Infrared spectroscopy shows the presence of BiO6and PO3structural groups and reveals the depolymerization of the phosphate links by the creation of the Bi–O–P groups. Replacing P2O5by Bi2O3shows that the dielectric constantɛr' and dielectric losses tanδvary with the concentration of added Bi2O3. Optical characteristics of the investigated glasses were determined using UV–vis spectroscopy and the energy band gap has been estimated.

Glass and Glass-Ceramics Based on Weathered Basaltic Rock for Radiation Shielding Applications

Different batches of weathered basalt ranging from 100 to 50 %, in combination with by-pass cement dust, were used to prepare the glass compositions. Different techniques utilized such as differential thermal analysis, X-ray diffraction, density, FTIR, the mass attenuation coefficients, appropriate atomic number (Zeff), and effective electron density (Neff), were examined for the prepared glass and glass-ceramics samples at different photon energies. In the present study, it was revealed that as the molar volume decreases, the density increases. The experimental and theoretical effects of the mass attenuation component were mostly consistent at different energies. The results revealed that glass samples (WB100) containing a higher percentage of basaltic rocks demonstrated higher radiation protection than those with lower rate (WB50). In addition, glass-ceramics displayed enhanced radiation and gamma rays protection than glass. Therefore, we recommend using glass- ceramics containing 100 % basalt as a protective shield against gamma rays with a lower thickness and higher protection.

Effect of Gd2O3 on the Structure and Dielectric Properties of Phosphobismuth Glass

In this study, 60P2O5–25Bi2O3-(10-x)CaO-5Sb2O3-xGd2O3 (x = 0, 1, 2, 3, 4 and 5) multi-component oxide glass was prepared by conventional high-temperature melting method. XRD spectrum indicates that all samples with x ≤ 3 mol% formed homogeneous glass, but the glass samples of x= 4 and 5 mol% had crystallized. The density, glass transition temperature (Tg), and softening temperature (Tf) of the doped 0–4 mol% Gd2O3 glass increased steadily, and the coefficient of thermal expansion (CTE) and molar volume decrease continuously. The IR spectra found that the glass network was denser and enhanced the structure when the sample contained 3 mol% Gd2O3. Homogeneous glass doped with 1–3 mol% Gd2O3 has better corrosion resistance than crystallized glass doped with 4 mol% Gd2O3. Dielectric constant (Ɛ) and dielectric loss (tanα) decrease as the network becomes compact. The glass containing 3 mol% Gd2O3 had a compact network structure and lower dielectric properties (Ɛ=5.01, tanα=2.6 × 10−3). The results show that Gd acts an important role in enhancing he cross-links between the phosphate chains and nd reducing the dielectric properties of the glass.

Ultrasonic Study of Molecular Interactions and Compressibility Behaviour of Samarium Soaps in Benzene-DMSO Mixture

Abstract: Ultrasonic measurements of samarium soaps (palmitate and myristate) have been carried out in a mixture of benzene and DMSO (70%-30% v/v) to determine the critical micellar concentration(CMC), soap-solvent interaction and various acoustic parameters. The results show that ultrasonic velocity, intermolecular free length, adiabatic compressibility, adiabatic molar volume and apparent molar compressibility decrease while specific acoustic impedance, relative association and solvation number increase with increase in soap concentration. The results of ultrasonic measurements have also been explained in terms of well-known equations. Keywords: Ultrasonic measurements, molecular interactions, samarium soaps, compressibility, critical micellar concentration(CMC).

Mixed modifier effect in lithium manganese metaphosphate glasses on the emission of highly dispersed Mn2+ centers for red-LED

Distribution of Mn2+ ions into lithium metaphosphate glass through modifier-site engineering is an effective approach to generate single-doped red phosphors for light emitting diodes (LED). This has been achieved through the systematic Li+-Mn2+ modifier mixing in xMnO‧(50-x)Li2O‧50P2O5 (0 ≤ x ≤ 50 mol%). In this regard, the mixed modifier effect on the structural and optical properties has been studied. While XRD demonstrates the amorphous structure of the prepared compositions, SAED reveals the formation of crystalline clusters in 50MnO‧50P2O5. XPS reveals that the ratio of BOs/NBOs (~0.5) is in agreement with that of theoretical stoichiometry. FTIR spectroscopy shows that the concentration of Q2 decreases, whereas Q1 increases. Also, it can be found that the density increases linearly with about 22% as the content of MnO increases. This is associated with a small decrease in molar volume (~3%). Overall, XPS, FTIR and density analyses indicate that Li+ and Mn2+ ions behave as network modifiers that resides in octahedral sites through the formation of LiO6 and MnO6, respectively. Indeed, there are strong absorption and excitation spectra due to the electronic transition in Mn2+. This results in an intensive orange-red emission around 608 nm (at x = 0.5) with a red-shift up to 684 nm (at x = 50) at excitation wavelength of 409 nm. This is ascribed to 4T1(G) → 6A1(S) electronic transition in the octahedrally coordinated Mn2+ ions with O2− anions. With increasing the MnO content, the emission is systematically intensified up to 10 mol% of MnO, and then quenched. This quenching is attributed to the increase in MnO6 groups, which cluster with each other. In these clusters, the electron transfer occurs between the neighboring Mn2+ ions. Furthermore, the independence of emission peak (shape and position) on the excitation wavelength demonstrates the presence of only high-dispersed Mn2+ activator center.

Structure, dielectric, and energy storage behaviors of the lossy glass-ceramics obtained from Na2O-Nb2O5-P2O5 glassy-system

ABSTRACT A series of phosphate glasses defined by the composition 50Na2O-xNb2O5-(50-x)P2O5 (0<x < 25 mol%) and designated as Nb5, Nb10, Nb15, Nb20, Nb25, respectively, have been elaborated by the melt quenching method, and their structural and optical properties were investigated. It was found that their density and molar volume increase and decrease with the Nb2O5 content, respectively. The analysis of the glasses structure by Raman spectroscopy allowed the identification of several phosphate structural units, mainly metaphosphate and pyrophosphate, and showed that niobium adopts an octahedral oxygen environment, forming linkages such as Nb-O-P and Nb-O-Nb within the network. Glass-ceramics were obtained by controlled heat treatments of the parent glasses. The heat treatment of the high niobium concentration glass Nb25 at 650°C led to the formation of the sodium niobate phase with cubic symmetry. Its microstructure was analyzed by SEM. The study of the dielectric properties of the glass-ceramics and their energy storage performance presented an optimum discharge density for the glass-ceramic with 25 mol% Nb2O5 and an energy efficiency of 82.5%.

Effect of Gd2O3 concentration on X-rays induced and photoluminescence characteristics of Eu3+ - Activated Gd2O3–B2O3 glass

Gd3+ doped borate glass samples with compositions of xGd2O3-(99-x)B2O3–1Eu2O3; (x = 20, 25, 30 and 35 mol%) (GdBEu) have been synthesized by melt-quenching method at 1400 °C for 3 h. GdBEu glasses characteristics have been determined via FTIR, absorption, emission (X-rays and UV excitation), and CIE color coordinates analysis. The GdBEu glasses presented density increase and molar volume decrease with Gd3+ ions. Ultraviolet (UV) and X-ray excitation have been indicated performance as well as luminescent properties of Gd2O3 doped glass structure. The 5D0 → 7F0 (582 nm), 5D0 → 7F1 (591 nm), 5D0 → 7F2 (616 nm), 5D0 → 7F3 (654 nm) and 5D0 → 7F4 (702 nm) were found at 275 nm and 394 nm excitations. The energy transfer phenomena from Gd3+→ Eu3+ in these glasses were observed. Intense reddish-orange emission were observed at 613 nm, which associated by energy transfer phenomena from Gd3+→ Eu3+ states in these glasses. The phonon sideband (PSB) and pure electronic transition (PET) were measured and calculated ponon energy of glasses. Decay time of GdBEu luminescence decreased with increase of Gd2O3 concentration. The Commission Internationale de l’Elcairage (CIE) color coordinates of GdBEu glasses displayed in reddish-orange region. X-rays induced luminescence presented 12% photon emission of GdBEu glasses comparing with BGO scintillation crystal.

Research on the Effects of Yttrium on Bismuth Titanate Borosilicate Glass System

Glasses with the chemical composition of 52B2O3 – 12SiO2–26Bi2O3 – (10 − x)TiO2 - xY2O3, :(0 ≤ x ≤ 10) prepared using the melt-quench method. The goal of this study is to investigate the structural, mechanical, and radiation shielding characteristics of these samples. XRD analysis has explored the nature of the glass system. Molar volume obtained reduced while the density denotes increased in the present system. As the molar volume decrease inter-ionic distance, polaron radius, inter-nuclear distance, and Y-Y separation of the investigated glasses decreased. The mechanical characteristics depend on the glass structure of the current glasses sample. Ultrasonic velocities and elastic moduli (experimental and theoretical) for these glasses obtained they were observed to get enhanced. The radiation shielding efficiency was investigated by Phy-X/PSD software. The mass attenuation coefficient, mean free path, half-value layer, tenth value layer, and effective atomic number of glasses have been designed to simulate gamma photon energies between 0.015 and 15 MeV.

Volumetric and viscosity behavior studies of Et4NBF4, Pr4NBF4, and Bu4NBF4 in acetonitrile solutions at T = (293.15–323.15) K

The thermodynamic and ion transporting properties of electrolyte solutions play a great role in electric double-layer capacitors (EDLCs). However, the related fundamental data and rules for many electrolyte solutions for EDLCs are still scarce. In this work, the volumetric and viscosity behaviors for tetraethylammonium tetrafluoroborate (Et4NBF4), tetrapropylammonium tetrafluoroborate (Pr4NBF4) and tetrabutylammonium tetrafluoroborate (Bu4NBF4) in acetonitrile (ACN) solutions have been investigated at 293.15–323.15 K. The standard molar volume and viscosity B coefficient of Et4NBF4, Pr4NBF4, and Bu4NBF4 have been calculated and their corresponding ion partial molar volume and ion viscosity B coefficients have been also discussed. It shows that both the standard partial molar volume and viscosity B coefficient of Et4NBF4, Pr4NBF4, and Bu4NBF4 in ACN solution decrease with the increased temperature, which suggests that Et4NBF4, Pr4NBF4, and Bu4NBF4 have strong interaction with ACN at low temperature than at high temperature, and the decrease of partial molar volume and viscosity B coefficient of solutions can be mainly ascribed to the interaction of anion and ACN molecules. Based on it, the contribution of solute and solvent to the Gibbs free energy of activation for the viscous flow have been discussed. These results will be helpful to further understand the ion and solvent interactions in new electrolyte systems and promote their design and commercial application.

Subsurface structural change of silica upon nanoscale physical contact: Chemical plasticity beyond topographic elasticity

Surface defects or flaws on materials made by physical contacts with foreign objects can deteriorate their mechanical properties and limit technical applications. Thus, understanding the contact-induced subsurface damage is of great importance. Using nanoscale infrared spectroscopy and reactive molecular dynamics simulations, the subsurface structural changes of silica upon nanoindentation and nanoscratch are investigated. The results reveal an elongation of the SiO bond length distribution even after the topographically-elastic contact, indicating a “chemical plasticity” at the sub-Angstrom level. In the plastic region with subsurface densification, the SiO bond is found to be slightly longer than the pristine region, indicating the decrease in molar volume is accompanied with the elongation, not shortening, of the SiO bond. These results elucidate the structural damage of a material upon physical contact cannot be delineated based on the topographic deformation of the surface.

Effect of Li2O content on structural and optical properties of Li2O-TeO2-As2O3-B2O3 glasses

Arsenate-based alkali borotellurite glasses with the general formula xLi2O-(30−x)TeO2-10A2O3-60B2O3, where 5 ≤ x ≤ 25, were formulated by the conventional melt quenching technique. The glassy nature of the samples was confirming by X-ray diffraction measurements. The influence of Li2O content on the Fourier transform IR, optical, and thermal properties, density, and other related properties of the prepared glasses was studied. The results reveal that the density and molar volume decrease and the glass transition temperature increases with increasing Li2O content This can be attributed to the difference in the ionic radii of lithium and tellurium oxides. The variation in the indirect optical bandgap and band tail with Li2O content is discussed in relation to the glass structure. On the basis of the values obtained for αO2−, the optical basicity, and the interaction parameter, the present glasses were termed normal ionic (basic) glasses. Fourier transform IR spectroscopy of the present glasses revealed that the borate network is affected by the replacement of TeO2 by Li2O. It was found that the fraction of four-coordinate boron atoms decreases and the fraction of three-coordinate boron atoms increases with increasing Li2O content.

DC electrical conduction in strontium vanadium borate glasses

Abstract A series of borate glasses with the composition x(SrO)·(50 – x)V2O5·0.5(B2O3) where x = 0, 0.1, 0.2, 0.3 and 0.4 were prepared by melt-quenching technique. The non-crystalline nature of the glasses has been established by XRD studies. Room temperature density and DC electrical conductivity of the samples were investigated in the temperature range of 300 K to 443 K. The molar volume and oxygen packing density (OPD) were estimated. The results show that the density, molar volume and OPD decrease with the increasing of SrO mole fraction. The DC electrical conductivity data has been analyzed in the light of Mott’s small polaron hopping (SPH) model and the activation energies were estimated. The conductivity was observed to rapidly fall and activation energy was found to increase when SrO was incorporated into the glass network. This may indicate that Sr+ ions have not contributed to the total conductivity and the observed conductivity may be of polaronic type only, which is due to the hopping of electrons between multivalent states of vanadium. Various small polaron hopping parameters such as small polaron radius, rp, effective dielectric constant, ϵp, polaron band width, J, optical phonon frequency, υo, small polaron coupling constant, γp, density of states at Fermi level, N(EF) were estimated and discussed.

Emergence of ferromagnetism due to charge transfer in compressed ilmenite powder using super-high-energy ball milling

Ilmenite, FeTiO3, is a common mineral in nature, existing as an accessory phase in the most basic igneous and metamorphic rocks, for example, it is derived from the upper mantle. Therefore, an understanding of the high-pressure physics of FeTiO3 is of fundamental importance in the study of rock magnetization. Here, we provide experimental evidence of lattice compression of FeTiO3 powder using super-high-energy ball milling, enabling the very high collision energy of 420 times gravitational acceleration. A sample obtained as an ilmenite- hematite 0.5FeTiO3·0.5Fe2O3 solid solution showed a decrease in molar volume of approximately 1.8%. Consequently, the oxidation state in FeTiO3 powder was changed into almost Fe3+Ti3+, corresponding to 87% Fe3+ of the total Fe for FeTiO3, resulting in the emergence of ferromagnetism. This new ferromagnetic behaviour is of crucial importance in the study of rock magnetization which is used to interpret historical fluctuations in geomagnetism. In addition, the super-high-energy ball mill can be used to control a range of charge and spin states in transition metal oxides with high pressure.

Eu3+ ions doped SrO-CaO-Li2O-B2O3glasses foroptical display material application

The glass systems with composition 20SrO-5CaO-40Li2O-(35-x) B2O3-x Eu2O3 (x = 0.3, 0.5 and 1 mol%) glasses were prepared by melt quenching technique to study absorption and luminescence properties and understand their lasing properties. Thepresent work reports the studies on Physical, Optical and luminescence properties of the prepared glass systems. The photoluminescence (PL) intensity of the glass increases with increase in Eu2O3 content up to 1mol%. The increase in the density and decrease in molar volume reveals the close packing of glass network. For Eu3+ emission the most intense red emission has been observed at the wavelength of 614nm for the transitions5D0 →7F2. The phonon energy was measured from phonon side band spectra which showed 1280cm−1, typical value for the borate glasses. Luminescence intensity ratio and lifetime analysis has been measured and discussed in the present work. The present glasses are very near to reddish orangeregion and thus can be key entrant for optical display device applications.

Investigation of Novel Low Melting Phosphate Glasses Inside the Na2O–K2O–ZnO–P2O5 System

Phosphate glasses containing different concentrations of zinc oxide inside the (1 − x)(NaPO3–KPO3)–xZnO system (0 ≤ x ≤ 50 mol%) have been prepared using the conventional melt quenching technique. The prepared glasses were transparent, bubble-free and colourless. Their density, molar volume, glass transition temperature, and structural properties using infrared and Raman spectroscopies are investigated. As the content of ZnO increases, the density increases while the molar volume decreases. The composition dependence of Tg shows a minimum for the glass (x = 20 mol%). Structural approach realized by IR and Raman spectroscopies reveals that zinc ions occupy different sites in the glassy-network, mainly modifier sites and middle phosphate network in low-zinc and high-zinc glasses, respectively. The introduction of ZnO in the network induces some structural rearrangements through the conversion of metaphosphate structural units to pyrophosphate ones. It is also highlighted that the presence of ZnO in the glassy matrix allows the transformation of some P–O–P and P=O bonds to P–O–Zn linkages. From the UV–Visible absorption studies, the values of the optical band gap, Eg, and Urbach energy, ΔE, were evaluated. The optical band gap is found to depend on the glasses composition. Eg and ΔE show a minimum and a maximum respectively, for the glass (x = 20 mol%).

Analysis of the Effect of Hydrostatic Pressure on the Nonvariant Eutectic Transformation in Al–Si, Al–Cu, and Al–Cu–Si Systems

Differential barothermal analysis (DBA) is used to analyze the effect of hydrostatic pressure of 100 MPa on characteristic temperatures of a number of eutectic alloys (wt %), such as Al–10Si, Al–12Si, Al‒22Cu, Al–33Cu, and Al–7Cu–7Si. According to DBA data, the increase in pressure resulted in an increase in the temperatures of phase transformation; in practice, the most important of them is the nonvariant eutectic transformation temperature that determines the solidus of alloys. It was found that, for the binary systems, the temperatures of the nonvariant eutectic transformation L → (Al) + Si and L → (Al) + Al2Cu increase by 6 and 11°С (from 577 to 583°С and from 548 to 559°С, respectively); for the ternary system, the temperature of transformation L → (Al) +Al2Cu + Si increases by 6°С (from 520 to 526°С). Theoretical analysis, performed using thermodynamic models and Thermo-Calc software, shows that the increase in the eutectic transformation temperature with increasing pressure is directly dependent on the relative decrease in the molar volume of system upon associated eutectic transformation. In this case, the excess dissolution of silicon in (Al) under high pressure can lead to an additional decrease in the molar volume of the system, whereas the increase in the copper solubility is thermodynamically unfavorable.

Synthesis and study of electrical properties of Li2O modified P2O5-ZnO-Na2O glasses

The transparent glasses of composition 40P2O5-20ZnO-(40-x)Na2O-xLi2O have been prepared using conventional melt quenching technique (where 0 ≤ x ≤ 25 Li2O mol. %). The amorphous nature of the prepared glass samples is confirmed by x-ray powder diffraction (XRD). By increasing the Li2O content, the density and oxygen packing density increase while the molar volume decreases which indicates that the structure is more compact. The differential thermal analysis (DTA) studies showes that 15 mol.% Li2O glass sample has the highest thermal stability and the glass transition temperature (Tg) decreases as the content of Li2O increases till 25 mol.% Li2O . The ac and dc electrical conductivities and dielectric constants of the prepared glass samples have been investigated. It is found that the dc conductivity increases with the concentration of Li2O mol.% and the temperature dependence of the dc conductivity at low temperature (303 – 383 K) and at high temperature (403 – 473 K) obey the Arrhenius law. The activation energies ΔEdc1 (at high temperatures) and ΔEdc2 (at low temperatures) were determined. The values of σdc can be obtained also from the impedance study at different temperatures and different concentrations using Cole-Cole plot. To determine the conduction mechanism, the ac conductivity and its frequency exponent (s) have been analyzed by correlated barrier hoping model (CBH). It is found that s has values between 0.89-0.996; consequently. The correlated barrier hopping (CBH) seems to be the most interesting model related to the obtained results. Real and imaginary parts of dielectric constant (e' and e'') have been found to decrease with increasing frequency and temperature and this result would be discussed by means of dielectric polarization mechanism of material. The maximum value of the maximum barrier height Wm obtained from Guitini equation was found to increase with increasing of Li2O mol. %.