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Physical properties of ZnF2–PbO–TeO2:TiO2 glass ceramics–Part III dielectric dispersion and ac conduction phenomena

In continuation of our earlier work on some physical properties (non-linear optical effects, piezoelectric and elastic properties) of ZnF2–PbO–TeO2:TiO2 glass ceramics, in the present study we have investigated the dielectric properties over a frequency range of 10-2 to 106 Hz and in the temperature range 303–523 K of these samples. The measurements include dielectric constant, ε′(ω), ac conductivity, σac, impedance spectra and electric modulus, M(ω). The temperature dispersion of real part of dielectric constant ε′(ω), has been analyzed using space charge polarization model. The ac conductivity exhibited maximal effect, whereas the activation energy for the conductivity demonstrated minimal value at 1.0 wt% of the crystallizing agent TiO2. In the low temperature region, the ac conductivity is nearly constant and varies linearly with frequency. Such behavior is explained following quantum mechanical tunneling (QMT) model. The dielectric relaxation effects for these samples have been analyzed quantitatively using the graphical method and spreading of relaxation times. The obtained results have been further analyzed quantitatively by Raman spectra. The variation of ac conductivity with the concentration of crystallizing agent was compared with second order susceptibility and the piezoelectric coefficient. The comparison indicated the phenomena responsible for the maximal effects for all the three parameters at 1.0 wt% of TiO2 are the same.

dielectric properties ; glass ceramics

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