Haque, Noor-ul- (1995) FABRICATION AND ELECTRICAL STUDIES OF SILVER BASED CONDUCTING GLASSES. PhD thesis, University of Karachi, Karachi.
The dielectric response of silver phosphate and silver borophosphate glasses has been investigated between 10-3-105 H2 with temperature and composition as parameters using a fully automated measuring system based on Solartron Frequency Response Analyser (1255 F.R.A). These oxide glasses were prepared and studied in three different configuration, viz. [(x) Ag2O(100-x)P2O5], [50Ag2O(x)B2O3 (50-x) P2O5] and [60Ag2O:(x)B2O3(40-X)P2O5] covering a wide range of low and high conducting glasses. It has been found that the domination of a quasi-direct current (Q-dc) process is the common feature of the dielectric spectra of these glasses. For a Q-dc process the real and imaginary components of the complex susceptibility follow fractional power law dependence on frequency with the exponent p less than, but close to unity. This incomplete transport of charge through limited paths between the electrodes causes an anomalously large frequency dependent polarisation and hence and hence capacitance. The studied silver based ion conducting glasses have shown a strong dependence on the composition of these glasses. It has been observed that the Q-dc region for [(x)Ag2O(100-X)P2O5] glasses is well developed at low frequencies and is followed b a frequency and temperature independent capacitance, C(ÃÂÃÂ¢ÃÂÃÂÃÂÃÂ) at higher frequencies. For [50Ag2O:(x)B2O3(50-X)P2O5) glasses a low frequency electrode phenomenon of Maxell-Wagner type has been found to overlap with a diplolar phenomenon at higher frequencies. Diffusive barrier regions have been found in [60Ag2O(x)B2O3:(40-X)P2O5) glasses with a characteristic lowest frequency slope of 0.5. It has been found that the gradual substitution of B2O3 in the glassy net-work influences the dielectric response and introduces an imperfect charge transport process (Q-dc) of limited charge transport in place of bulk conduction, at higher frequencies and effects the diffusion barrier at the electrodes to make them, slightly more conductive at the lowest frequencies for [60Ag2O(x)B2O3:(40-X)P2O5) glasses. The magnitudes of the activation energies of conduction and dielectric relaxation have been found approximately same ad have been attributed to a closely related thermally activated localized hopping mechanism of silver ions between the neighboring sites. The power law dispersions for the bulk and the surface layer of [Ag2O:B2O3:P2O5] glasses have also been modeled mathematically using frequency dependent resistive and capacitive elements in a conventional equivalent R-C network. A response function, C(ÃÂÃÂÃÂÃÂ) (iÃÂÃÂÃÂÃÂ) ÃÂÃÂ¢ÃÂÃÂÃÂÃÂP /[1+(iÃÂÃÂÃÂÃÂ) S-P] with both the exponents p and s positive and less than 1 has been proposed which successfully modeled the experimentally observed dielectric response.
|Item Type:||Thesis (PhD)|
|Uncontrolled Keywords:||silver based conducting glasses, dielectric polarisation, insulators, conductor, glass, glass transition, borophosphate glasses, borate glasses, phosphate glasses, thermal characterization|
|Subjects:||Physical Sciences (f) > Physics(f1)|
|Deposited By:||Mr. Muhammad Asif|
|Deposited On:||27 Oct 2006|
|Last Modified:||04 Oct 2007 21:02|
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