2011 - Electrical, dielectric and structural properties of borovanadate glass systems doped with samarium oxide.pdf (original) (raw)
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We report on the structural, morphological and optical characterization of glass and glass–ceramic samples , with nominal composition of 91SiO 2 :4Li 2 O:4Nb 2 O 5 :1Dy 2 O 3 (% mole). The samples were heated treated in air in the temperature range between 500 °C and 800 °C. The glass–ceramics samples start to crystallize at temperatures above 600 °C and besides the SiO 2 and LiNbO 3 crystalline phases, sub micron DyNbO 4 precipitates were identified by X-ray diffraction and scanning electron microscopy for temperatures above 750 °C. Using Raman spectroscopy was possible to identify the vibration modes assigned to the crystalline phases detected by the XRD analysis. Also, the performed Photoluminescence Spectros-copy analysis suggest that the optical activation of Dy 3+ ions in the glass and glass–ceramics hosts was found to be dependent of the heat treatment temperature. Intraconfigurational transitions between the 4 F 9/2 and 6 H J(=15/2, 13/2) multiplets of Dy 3+ ions were only observed for samples without the presence of the DyNbO 4 crystalline phase. Moreover, for samples heat treated between 500 °C and 700 °C the intensity ratio of the 4 F 9/2 6 H 13/2 and 4 F 9/2 6 H 15/2 transitions of the lanthanide ion changes, suggesting different ion environments which are dependent on the thermal annealing temperature. The dielectric measurements revealed that e 0 value depends mainly in the number of network modifier ions and the relaxation phenomenon observed at frequencies above 10 kHz, in all samples, can be assigned to the increase of the volume ratio between the LiNbO 3 particles and the glass network.
A study of the structural, spectroscopic, and dielectric properties of La2O3 doped borate glass
Journal of Materials Science: Materials in Electronics, 2017
The La 2 O 3 doped borate glass of composition [B 2 O 3 +Li 2 Co 3 +Zno+Sr 2 O 3 +H 6 No 4 P+Y 2 O 3 +La 2 O 3 ] was prepared by melt quenching method. The appropriate quantities of B 2 O 3 , Li 2 Co 3 , ZnO, Sr 2 O 3 , Y 2 O 3 and La 2 O 3 were weighed and mixed together with a morter, to get fine powder. All the chemicals were of 99.99% of purity purchased from Sigma Aldrich. The desired mixture was taken in a silica crucible and heated in a muffle furnace at 1300 °C for 3 h. The sample was melted at 1170 °C, and suddenly Abstract We have synthesized La 2 O 3 doped borate glasses using conventional rapid melt quench method. The amorphous nature was identified using the X-ray diffraction pattern. Photoluminescence spectrum and IR spectrum were used to analyze the optical properties and differentiate the various vibrational modes. Also Raman spectroscopy of La 2 O 3 doped borate glass was studied. The electrical properties such as the dielectric constant, the dielectric loss, and AC conductivity of the La 2 O 3 doped borate glass were studied at different frequencies and different temperatures.
Journal of Non-crystalline Solids, 2017
Lithium sodium fluoroborate glasses doped with vanadium ions were prepared by melt annealing technique. The structural investigation shows the formation of probable BO 3 , BO 4 , BO 2 F, and BO 3 F structural units. Moreover, vanadium ions are mostly presented in such glasses as V 4 + state and it may form non-bridging oxygens (NBOs). The decreasing in the optical band gap values as a function in the glass composition or vanadium content approves the formation of NBOs. The refractive index is estimated directly from the optical band gap values by using the Dimitrov-Sakka relation. Density, molar volume, molar refraction, and metallization criterion were studied and explained in terms of the structural changes obtained by the impact of the vanadium ions. Thermal activation energy is explained by the formation of Non-bridging oxygens and the effect of V 2 O 5 dopant.
Influence of rare-earth ion doping on dielectric properties of lithium zinc borate glasses
The dielectric constant (ε ′), loss factor (tanδ), and ac conductivity (σ ac) of 30 Li 2 O-10 ZnO-(60-x) B 2 O 3 : xLn 2 O 3 , where (x = 0 and 1) and (Ln = Pr, Nd, Sm, and Eu) were investigated using a frequency range of 10 2-10 5 Hz and temperature ranging from 30 to 250 • C in this work. Differential Scanning Calorimetry (DSC) technique was employed to confirm the glassy nature of the materials under study. The dielectric parameters ε ′ , tanδ, and σ ac rise when rare-earth ions are added to the glass matrix at any frequency or temperature. Dielectric breakdown and activation energies are lower in doped than in undoped glasses while ac current flows through them at room temperature. Rare-earth ion doping's dielectric parameter values decrease with temperature as atomic number (Z) rises. The dielectric parameter values for the Pr 3+ doped glass matrix are the highest. QM tunnelling model was used to describe the ac conduction behaviour of these glasses.
Electrical Properties of Lithium and Sodium Borate Glasses Doped with Chromium Oxide
Background: In this work, we experimentally studied the ac-electric conductivity and dielectric constant of some lithium and sodium borate glasses doped with chromium oxide. These glass materials are of interest for science and technology. Materials and Methods: We introduced Chromium oxide with Low concentration of 0.1 and 0.7 mol. % to Lithium and Sodium borate glasses with chemical composition 37 mol % [M 2 O]-63 mol % [B 2 O 3 ] where (M=Li and Na)]).We successfully prepared the glass samples by melting quenching method. The X-ray diffraction pattern was carried out using Bruker AXS X-Ray analytical diffraction system. The ac-electrical conductivity, and dielectric constant measured at atmospheric pressure as a function of temperature (in the range from room temperature up to 500 0 K) and frequency in the range from 0.1 kHz up to 200 kHz). Results: The X-ray patterns showed the amorphous nature of these glasses. The curve features of the ac-conductivity showed deviations from the Arrhenius linear relation observed at T < 400 K. We estimated the crystalline activation energies for all samples under consideration. The measurements verified the scaling law of the ac-conductivity as a function of the applied frequency. Conclusion: From the results, we have the following: a) From the recorded XRD Spectra we observed evidence of the formation of pre-crystalline phase; b) The electrical properties of these glasses are affected by the different physical and chemical processes; c) Values of the ac-conduction mechanism are predominantly ionic in the undoped samples containing Li or Na ions. The mobility of these ions is affected by the presence of Cr ions in all doped samples; d) The increase of the ionic mobility is responsible for the behaviour of the dielectric loss of these glass samples.
Electrical, dielectric, and optical properties of Sb2O3–Li2O–MoO3 glasses
Journal of Non-Crystalline Solids, 2015
Temperature and frequency dependencies of DC and AC conductivities, dielectric response, static permittivity, optical absorption edge, infrared absorption spectrum, density, and temperatures of glass transition and crystallization for lithium molybdenum-antimonite glasses, (80 − x)Sb 2 O 3 -20Li 2 O-xMoO 3 , where x = 0-40, are measured and discussed. The DC conductivity increases with increasing concentration of MoO 3 . At 150°C, it ranges from 5 × 10 −11 S/m up to 3 × 10 −8 S/m. Polaron hopping between Mo 5+ and Mo 6+ ions contributes, probably, to the DC conductivity. Ionic conductivity by Li + ions is also present. The conduction activation energy monotonously decreases from 1.15 eV, at x = 5, down to 0.91 eV, at x = 40. In all glasses with x N 0, the conduction activation energy is close to a half of the indirect allowed optical gap. The pre-exponential factor, σ 0 , goes through a sharp maximum close to the composition (x = 20) with both the highest glass transition temperature and the largest thermal stability range. The frequency dependence of the AC conductivity is composed of three componentsthe DC conductivity and two AC components. For x = 35 and 40, the activation energy of electrical relaxation is equal to 0.954 ± 0.008 eV and the pre-exponential factor of relaxation times is equal to (4 ± 1) 10 −14 s. The static relative permittivity ranges from 17.4 to 23.0. Strong extrinsic absorption bands in infrared region originate from hydroxyl ions, CO 2 impurities, and silicon-oxygen vibrations. The UV-visible indirect allowed absorption edge shifts from 2.6 eV to 2.1 eV with increasing MoO 3 content. With increasing MoO 3 content the glasses darken, from a light yellow color, at x = 0, to a deep brown color, at x = 40.
A comparative study on lanthanum oxide and holmium oxide doped borate glasses
Glass Physics and Chemistry, 2017
⎯We have synthesized La 2 O 3 and Ho 2 О 3 doped borate glasses using conventional rapid melt quench method. The amorphous nature was identified using the XRD pattern. Photoluminescence spectrum and IR spectrum were used to analyze the spectral properties and differentiate the various vibrational modes. Also Raman spectroscopy of La 2 O 3 and Ho 2 О 3 doped borate glass was studied. The electrical properties such as the dielectric constant and the dielectric loss, of the La 2 O 3 and Ho 2 О 3 doped borate glass were studied at different frequencies and different temperatures.