Buchi Suresh M* and Roy Johnson
Centre for Ceramic Processing, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad, Telangana, IndiaFulltext PDF
ZnAl2 O4 spinel ceramics were synthesized by solid state reaction from stoichiometric mixture of precursor oxides such as ZnO and Al2 O3 . Phase pure ZnAl2 O4 powder was compacted and the specimens were subjected to sintering experiments. The dilatometric curves indicated a prominent densification regime. Sintered samples were characterized by XRD, SEM, thermal expansion and high temperature complex impedance spectroscopy. X-ray pattern showed cubic spinel phase with crystallite size of 40 nm. Dilatometric analysis resulted into a thermal expansion of 8.4 × 10-6/°C (RT-1,000°C). High temperature dielectric and complex impedance spectroscopic analysis of the ceramics have been investigated in the frequency range from 1 Hz to 1 MHz and temperature range from 300°C to 700°C. Experimental results revealed the decrease in dielectric constant (er ) and real part of impedance (Z’) with frequency and an increase in electrical conductivity with frequency. Imaginary part of impedance (Z”) reaches to a maximum value with increasing frequency and thereafter decreases with further increase in frequency. The complex impedance analysis suggests predominant conduction is due to grain and grain boundaries. Activation energy obtained from the conductivity plot indicates an Arrhenius type thermally activated process due to oxygen vacancies suggesting the conduction by hopping mechanism. SEM image revealed a highly dense microstructure with well bounded grains with average grain size of 3.5 mm
Dielectric constant; Impedance spectroscopy; Conductivity; Spinel; Thermal expansion
Buchi Suresh M, Johnson R. Synthesis and High Temperature Dielectric and Complex Impedance Spectroscopic Studies of Dense ZnAl2 O4 Ceramics. Mater Sci Eng J. 2017;1(1):1001.