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ZnO/TiO2 composite ceramics have been prepared by solid-state reaction technique at 900°C. The X-ray diffraction results revealed the formation of secondary phases referred to as spinel Zn2TiO4 and hexagonal ZnTiO3. The structural analysis showed that all the composites that have been prepared have a polycrystalline nature and a hexagonal wurtzite structure. The complex modulus ( M) and electric impedance of the samples have been investigated by broadband dielectric spectroscopy in a wide range of temperature (40°C-110°C) and frequency (0.1 Hz to 10 MHz). The modulus plots (M′′, M′) illustrate the presence of non-Debye type of relaxations attributed to the effects of interfacial and dipolar polarizations. The real and the imaginary parts of the impedance are well fitted to equivalent circuit models. At high temperatures, Z″max varies from 0.03 × 106 to 4.9 × 106 Ω when the TiO2 doping concentration increases from 1 to 7 wt%. From the obtained results, the secondary phase ZnTiO3 plays an important role in the electrical properties. [ABSTRACT FROM AUTHOR]

Undoped zinc oxide has been prepared at various growth temperatures by a conventional sintering process. The crystal structures of the prepared samples were studied by X-ray diffraction. The frequency-dependent dielectric dispersion of all the sintered ZnO ceramics was investigated in the temperature range from −100 to 30 °C and in the frequency range from 1 Hz to 10 MHz by broadband dielectric spectroscopy. An analysis of the complex permittivity and electric modulus as a function of frequency has been performed assuming a distribution of relaxation times. The pellet sintered at 900 °C showed the lowest value of the dielectric strength. The temperature dependent of the parameter α is discussed. While the charge transport through the grain and grain boundary regions was examined by impedance spectroscopy. Activation energy values extracted from conduction measurements were found to be in the range of 0.09 and 0.3 eV. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effects of different Sn2O3 doping concentrations were investigated. [•] Band gap broadens if the doping concentration increases. [•] The increase in Sn2O3 content, superior or equal to 10wt%, the dielectric loss disappears. [•] The dc conductivity increases with the increase of Sn2O3 doping concentrations. [•] The temperature dependent ac conductivity follows the universal power law. [ABSTRACT FROM AUTHOR]

Abstract: A series of Zinc Oxide pellets sintered at different temperatures was studied by means of dielectric spectroscopy in the wide frequency range of 1–106 Hz and temperature interval from −100°C to 30°C. Electrical conductivity was analysed using Jonsher''s universal power law, and the values of s were found to decrease with the increase in temperature, which agrees well with the correlation barrier hopping (CBH) model. As the temperature increased, energy activation E dc became less than 0.39eV and dc conductivity (σ dc ) values in the range of 1.9×10−14–9.7×10−10 Ωm−1 were observed. The dielectric modulus showed ionic polarisation at the intermediate and high frequencies related to oxygen interstitial O i , oxygen vacancy V O and Zinc interstitial Zn i . At low frequency, it revealed a Maxwell–Wagner–Sillars relaxation with barrier heights of grain boundaries between 0.74 and 0.88eV for all the studied pellets. [Copyright &y& Elsevier]