Relaxation and conductivity properties of xSrBi2Nb2O9–(1−x)Li2B4O7 glasses (original) (raw)
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A transparent glass with the composition 60B 2 O 3 –30Li 2 O–10Nb 2 O 5 (mol%) was prepared by the melt quenching technique. The glass was heat-treated with and without the application of an external electric field. The as-prepared sample was heat-treated (HT) at 450, 500 and 550 °C and thermoelectric treated (TET) at 500 °C. The following electric fields were used: 50 kV/m and 100 kV/m. Differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, dc and ac conductivity, as a function of temperature, were used to investigate the glass and glass-ceramics properties. LiNbO 3 crystals were detected, by XRD, in the 500 °C HT, 550 °C HT and 500 °C TET samples. The presence of an external electric field, during the heat-treatment process, improves the formation of LiNbO 3 nanocrystals at lower temperatures. However, in the 550 °C HT and in the TET samples, Li 2 B 4 O 7 was also detected. The value of the r dc decreases with the rise of the applied field, during the heat-treatment. This behavior can indicate an increase in the fraction of the LiNbO 3 crystallites present in these glass samples. The dc and ac conduction processes show dependence on the number of the ions inserted in the glass as network modifiers.The Raman analysis suggests that the niobium ions are, probably, inserted in the glass matrix as network formers.These results reflect the decisive effect of temperature and electric field applied during the thermoelectric treatment in the structure and electric properties of glass-ceramics.
Dielectric properties of Li2O3B2O3 glasses
Journal of Applied Physics, 2009
The frequency and temperature dependence of the dielectric constant and the electrical conductivity of the transparent glasses in the composition Li 2 O-3B 2 O 3 (LBO) were investigated in the 100 Hz-10 MHz frequency range. The dielectric constant and the loss in the low frequency regime were electrode material dependent. Dielectric and electrical relaxations were respectively analyzed using the Cole-Cole and electric modulus formalisms. The dielectric relaxation mechanism was discussed in the framework of electrode and charge carrier (hopping of the ions) related polarization using generalized
Electrical transport properties of 0.5Li2O–0.5M2O–2B2O3 (M=Li, Na and K) glasses
Journal of Non-Crystalline Solids, 2011
Transparent glasses in the system 0.5Li 2 O-0.5M 2 O-2B 2 O 3 (M=Li, Na and K) were fabricated via the conventional melt quenching technique. Amorphous and glassy nature of the samples were confirmed via the X-ray powder diffraction and the differential scanning calorimetry, respectively. The frequency and temperature dependent characteristics of the dielectric relaxation and the electrical conductivity were investigated in the 100 Hz-10 MHz frequency range. The imaginary part of the electric modulus spectra was modeled using an approximate solution of Kohrausch-Williams-Watts relation. The stretching exponent, β, was found to be temperature independent for 0.5Li 2 O-0.5Na 2 O-2B 2 O 3 (LNBO) glasses. The activation energy associated with DC conductivity was found to be higher (1.25eV) for 0.5Li 2 O-0.5K 2 O-2B 2 O 3 (LKBO) glasses than that of the other glass systems under study. This could be attributed to the mixed cationic effect.
Author's personal copy Conductivity and dielectric relaxation in niobium alkali borate glasses
The frequency and temperature dependent conductivity investigations for alkali niobium borate glasses of composition xNb 2 O 5 Á (30 À x)M 2 O Á 70B 2 O 3 (where M ¼ Li, Na; x ¼ 0, 4, 8 mol%) have been carried out using impedance spectroscopy (IS). The complex impedance data have been analyzed by using both the conductivity and the electric modulus formalisms. The conductivity decreases with the decrease in M 2 O:Nb 2 O 5 ratio. The effect of temperature on the scaling of dielectric modulus indicates that the conductivity relaxation mechanism is temperature independent. The overlapping of the normalized peaks corresponding to impedance and electric modulus and the identical values of thermal activation energy for conduction and relaxation suggest the single mechanism for the dynamic processes occurring in the present glasses. The variation of density, molar volume and glass transition temperature with glass composition has also been reported to supplement the conductivity results.
The preparation and properties, of nanocrystals embedded in a glass matrix have recently received a considerable amount of interest. The glass composition 92SiO 2 –4Li 2 O–4Nb 2 O 5 (mol%), prepared by the sol–gel route gives origin to a transparent and col-orless gel. The dried gel was heat-treated at temperatures between 500 and 750 °C, with and without the presence of an external electrical dc field. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Raman and dielectric spectroscopy were used to characterize the glass samples. In the samples heat-treated at 650 °C with 1000 kV/m and in the 700 and 750 °C samples series, LiNbO 3 crystallites, an important ferroelectric material is present. The behavior of the dc conductivity and the dielectric constant , in the glass and glass-ceramic, reflects the important effect of the temperature and the applied electric field on the sample structure.
Electrical properties of lithium niobium silicate glasses
Lithium niobate (LiNbO 3) is a ferroelectric material in the crystalline form and considerable interest has recently been shown in the study of its properties in a glass structure. A 34SiO 2 –33Li 2 O–33Nb 2 O 5 (mol%) glass was prepared using the conventional melt-quenching method. LiNbO 3 crystals were precipitated in the glass matrix by a heat-treatment (HT) process. These glasses were studied by differential thermal analysis, X-ray power diffraction (XRD), scanning electron microscopy, dc electrical conductivity (r dc), ac conductivity (r ac) and dielectric measurements. LiNbO 3 crystal phase was detected by XRD on the sample HT at 600 °C. The dc and ac conductivity, at 300 K, decreases with the increasing of the HT temperature. The dielectric study in function of frequency, at constant temperature , was made using the modulus (M Ã) model and a distribution of relaxation times was observed. The dielectric data was fitted with the complex non-linear least squares procedure, revealing that a resistor in parallel with a constant phase element is the best equivalent circuit. The dielectric constant value, measured at 1 kHz and room temperature, decreases from 102 to 62 with the increasing of the HT temperature, suggesting a random orientation of the dipolar moments associated with the LiNbO 3 nanocrystals.
Conductivity and dielectric relaxation in niobium alkali borate glasses
Physica B-condensed Matter, 2010
The frequency and temperature dependent conductivity investigations for alkali niobium borate glasses of composition xNb 2 O 5 Á (30 À x)M 2 O Á 70B 2 O 3 (where M ¼ Li, Na; x ¼ 0, 4, 8 mol%) have been carried out using impedance spectroscopy (IS). The complex impedance data have been analyzed by using both the conductivity and the electric modulus formalisms. The conductivity decreases with the decrease in M 2 O:Nb 2 O 5 ratio. The effect of temperature on the scaling of dielectric modulus indicates that the conductivity relaxation mechanism is temperature independent. The overlapping of the normalized peaks corresponding to impedance and electric modulus and the identical values of thermal activation energy for conduction and relaxation suggest the single mechanism for the dynamic processes occurring in the present glasses. The variation of density, molar volume and glass transition temperature with glass composition has also been reported to supplement the conductivity results.
Glass and glass-ceramics with the molar composition of 60SiO 2 –30Li 2 O–10Nb 2 O 5 (mole %) were studied. Ferroelectric lithium niobate (LiNbO 3) nanocrystals were precipitated in the glass matrix trough a thermal treatment, with and without the simultaneous application of an external electric field. The as-prepared sample, yellow and transparent, was heat-treated (HT) at 600 and 650 °C and thermoelectric treated (TET) at 600 °C. The applied electric fields were the following ones: (i) 5 · 10 4 V/m; (ii) 1 · 10 5 V/m. Differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and dielectric spectroscopies were used to investigate the glass samples properties. The LiNbO 3 crystalline phase was detected in the 650 °C HT sample and in the 600 °C TET samples. The presence of an external electric field, during the heating process, promotes the glass crystallization at lower temperatures. In the TET samples, the surface crystallization of the cathode and the anode are different. The number and size of the crystallites, in the glass network, dominate the electrical dc behavior while the ac conductivity process is more dependent of the glass matrix structure. The obtained results reflect the important role carried out by the temperature and the applied electric field in the glass-ceramic structures.
ELECTRICAL CONDUCTIVITY AND DIELECTRIC RELAXATION OF LITHIUM ALUMINO BORATE GLASSES
Ion conducting glasses 30 Li2O: (70-X) B2O3): X Al2O3 have been prepared over wide range composition (x = 0, 5, 10, 15 and 20 mole %). The mixed former effect on lithium ion transport due to addition of Al2O3 in series of Lithium borate glasses have been investigated. The electrical conductivity and dielectric relaxation of these glasses was analyzed using Aligent LCR analyzer in frequency range (1Hz – 1MHz) at different temperature (323k – 623k). The decrease in conductivity with the addition of Al2O3 attributed to structural modification and formation of B – O – Al Linkage resulting in reduces migration of Li+ ions along these bonds. The dielectric constants and modulus formalism is used to described the dielectric relaxation.
Dielectric relaxation in glass and glass‐ceramic materials of the system La2O3‐Gd2O3‐PbO‐MnO‐B2O3
International Journal of Applied Glass Science, 2018
The electrical properties of new borate‐based glasses in the system La2O3‐Gd2O3‐PbO‐MnO2‐B2O3, prepared by the melt‐quenching technique, were investigated. All of these glasses have a fixed content of B2O3 (%mol = 30). The electrical measurements were carried out by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz, and temperatures from 100 to 400°C, below the glass temperature. The AC conductivity increases with temperature according to the Arrhenius law, with a single activation energy. The structural and thermal properties of the glasses were investigated by performing infrared spectroscopy, X‐ray diffraction, and differential thermal analysis. The dependence of the various electrical parameters as a function of the glass composition and temperature was discussed. Evaluations of models and theory of the relaxation mechanisms were predominantly made through comparison with experimental data and a set of phenomenological parameters.