Structural, electrical and dielectric characteristics of strontium-modified CaCu3Ti4O12
In order to produce an ultra-high dielectric constant and low loss factor in a polycrystalline material of Sr+2-modified (concentration 15%) CaCu3Ti4O12 (i.e., Ca0.85Sr0.15Cu3Ti4O12, abbreviated as CSCTO-15) was prepared using a cost-effective solid-state reaction technique. Structural analysis using Rietveld refinement of the X-ray diffraction data has confirmed that the sample crystallizes in a cubic system with space group symmetry of Im3. Morphological/microstructural analysis of the natural surface of a pellet shows dense grain growth, with clearly visible grain boundaries. The dielectric relaxation mechanism of CSCTO-15 has been revealed by the detailed study of frequency- and temperature-dependent dielectric parameters (εr and tan δ). Analysis of the frequency and temperature dependence of impedance and related parameters, collected by a complex impedance spectroscopic technique, has provided and estimated the contributions of grain, grain boundaries and electrode in the electrical process in the material. The activation energy at high temperatures has been calculated from the temperature-dependent ac conductivity plots at selected frequencies.