Preparation and study of dielectric proprieties of glassy materials in ternary system Bi2O3-Nb2O5-P2O5 (original) (raw)
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Structural and electric-dielectric properties of some bismuth -phosphate glasses
Journal of Physics and Chemistry of Solids, 2012
In the present study, glasses with composition XBi 2 O 3 (60 À X)P 2 O 5 20Fe 3 O 4 20Li 2 O (0r X r 15) mol% have been prepared by the conventional melt quenching technique. The IR studies show the presence of FeO 4 , FeO 6 , BiO 6 , PO 3 , PQO and PO 4 structural groups. The hyperfine structure of these glasses is investigated using Mössbauer spectroscopy. ME spectroscopy indicated the presence of two different oxidation states of iron (Fe 2 þ and Fe 3 þ ). The ferrous ions Fe 2 þ occupied tetrahedral coordination states, while the ferric ions Fe 3 þ occupied both tetrahedral and octahedral coordination states. The effect of partial replacement of P 2 O 5 by Bi 2 O 3 on the electric-dielectric properties is studied in more details. It is found that, unmonotonic variation in the s dc , (y D /2), s ac (o), e 1 (o), and e 2 (o), as a function of Bi 2 O 3 contents. Also it is found that, the power law exponent, s, is temperature dependent and the CBH model is the most applicable conduction mechanism in all glass samples. Pseudo Cole-Cole diagram of the investigated glassy samples exhibit similar behavior where all plots show a single semicircle indicating a single relaxation process.
Electrical conduction and dielectric properties of Bi2O3–B2O3–TeO2 glass
Journal of Materials Science, 2014
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Journal of applied physics, 2009
X-ray powder diffraction along with differential thermal analysis carried out on the as-quenched samples in the 3BaO-3TiO 2 -B 2 O 3 system confirmed their amorphous and glassy nature, respectively. The dielectric constants in the 1 kHz-1 MHz frequency range were measured as a function of temperature ͑323-748 K͒. The dielectric constant and loss were found to be frequency independent in the 323-473 K temperature range. The temperature coefficient of dielectric constant was estimated using Havinga's formula and found to be 16 ppm K −1 . The electrical relaxation was rationalized using the electric modulus formalism. The dielectric constant and loss were 17Ϯ 0.5 and 0.005Ϯ 0.001, respectively at 323 K in the 1 kHz-1 MHz frequency range which may be of considerable interest to capacitor industry.
Near Constant Loss Dielectric Response in 2Bi2O3-B2O3 Glasses
International Journal of Applied Glass Science, 2011
Electrical conduction and relaxation phenomena in bismuth borate glasses in the composition 2Bi 2 O 3-B 2 O 3 (Bi 4 B 2 O 9) were investigated. Dielectric studies carried out on these glasses revealed near constant loss (NCL) response in the 1 kHz to 1MHz frequency range at moderately high temperatures (300-450K) associated with relatively low loss (D=0.006) and high dielectric constant (ε r '=37) at 1kHz,300K. The variation in AC conductivity with temperature at different frequencies showed a cross over from NCL response characterized by local ion vibration within the potential well to universal Joncher's power law dependence triggered by ion hopping between potential wells or cages. Thermal activation energy for single potential well was found to be 0.48±0.05eV from cross over points. Ionic conduction and relaxation processes were rationalized by modulus formalism. The promising dielectric properties (relatively high ε r ' and low D) of the present glasses were attributed to high density (93 % of its crystalline counterpart), high polarizability and low mobility associated with heavy metal cations, Bi 3+ .
Dielectric properties and structural features of barium-iron phosphate glasses
Journal of Non-Crystalline Solids, 2004
The dielectric constant of barium-iron phosphate glasses with the general composition (40)x)BaO AE xFe 2 O 3 AE (60)x)P 2 O 5 has been investigated at two fixed frequencies (100 kHz and 9.0 GHz). The dielectric constant measured using microwave technique, and the ratio O/P of these glasses increase with increasing Fe 2 O 3 content. The structure and valence states of the iron ions in these glasses were investigated using M€ ossbauer spectroscopy, infrared spectroscopy and differential thermal analysis. Both Fe(II) and Fe(III) ions present in these glasses in octahedral coordination act as permanent dipoles, and the increase of the iron concentration increase these permanent dipoles, contributing to the dielectric constant.
The dielectric properties of TeO 2–P 2O 5 glasses
Materials Chemistry and Physics, 2000
The dielectric constant and the tangent loss were measured for the TeO 2 -P 2 O 5 glass system in the frequency range 0.1-10 kHz at different isotherms. The dielectric constant and the tangent loss decreased with increasing frequency, while both of them increased with increasing temperature. The decrease of the dielectric constant with increasing frequency was attributed at low frequency to the contribution of all the polarizability components, while at higher frequencies the absence of ionic and orientational polarizability components. The increase of the dielectric constant with temperature was due to the combination of electronic, ionic and orientational polarizability components. The decrease of the loss factor with increasing frequency was attributed at low frequency mainly to the migration of ions in addition to the electronic polarization loss, while at high frequency the ion vibrations may be the only source of the dielectric loss. The increase of the loss factor with increasing temperature was attributed to the relaxation loss in addition to the conduction loss which increased more rapidly with temperature.
Dielectric behaviour of glasses and glass ceramics in the system BaO-PbO-TiO2-B2O3-SiO2
Bulletin of Materials Science, 1987
Glasses wflh varying molar ratios of PbO/BaO in the system BaO-PbO-TiO z-B2Os-SiO 2 were prepared keeping (BaO + PbO)/TiO 2 ralio equal to one. The glasses were ccramized by lwo-slage heat treatment. X-ray diffraction indicales that PbTiO 3 crystallizes in lead-rich glasses while BaTiO 3 precipilates in barium-rich compositions. Solid solution (Ba, Pb)TiO s does not seem to crystallize over the entire range of compositions. Simultaneous presence of PbO and BaO in the initial glass composition reduces the yield of ferroelectric phase. Dielectric properties have been interpreted in terms of microstructural features.
Dielectric Dispersion in PbO-Bi2O3-B2O3 Glasses Mixed with TiO2
Turkish Journal of …, 2008
[(PbO)0.20−x•(Bi2O3)0.40•(B2O3)0.40]:(TiO2)x, 0.0 ≤ x ≤ 0.02 glasses were prepared. Dielectric properties (dielectric constant ε , loss tan δ and a.c. conductivity σac, over a wide range of frequency and temperature), optical absorption, ESR and IR spectra of these glass materials have been investigated. The dielectric study has revealed that the glasses possess high insulating strength when TiO2 concentration is >0.8 mol% in the glass matrix. The optical absorption spectra of these glasses exhibited bands due to Ti 3+ ions in the visible region. ESR spectral studies have also indicated that a fraction of Ti 4+ ions reduced to Ti 3+ ions. IR spectra of these glasses exhibited bands due to TiO4 and TiO6 structural units. Quantitative studies indicate that as concentration of TiO2 is increased to 0.8 mol% in the glass matrix, a large proportion of titanium ions exist in Ti 3+ state and has influenced the physical properties of these glasses to a substantial extent.
Journal of the European …, 2004
Vitrification and crystallization properties of glasses of the system BaO-TiO 2 -PbO-Al 2 O 3 (B 2 O 3 ) were investigated. The fields of vitrification based on ternary diagrams of BaTiO 3 -PbTiO 3 -(TiO 2 +Al 2 O 3 +B 2 O 3 ) with varied contents of Al 2 O 3 (10, 13, 16 mol.%) and B 2 O 3 (3, 15 mol.%) were identified. The glass compositions obtained had relatively low melting temperature (%1450 C). These stable glasses could be thermally treated to produce glass-ceramics characterized by fine-crystalline structures and regulated permittivity associated to the contents of ferroelectric phases. The phase composition of such glass-ceramics included different Pb x Ba 1-x TiO 3 solid solutions depending on the starting chemical composition. Permittivity of the obtained materials (f=800 kHz, T=25 C) varied from 20 to 680 relatively to the time of crystallization. #