An approach for correlating electrically heterogeneous structure to enhanced dielectric properties of Sr and Zn co-substituted CaCu3Ti4O12 ceramics

In the present work, the most pristine as well as strontium (Sr) and zinc (Zn) modified Calcium copper titanate ceramics having formula Ca0.95Sr0.05Cu3Ti4-xZnxO12 (x = 0.01, 0.025, 0.05 & 0.10) were synthesized by the solid state reaction method. X-ray diffraction pattern and Raman analysis confirmed the single phase formation of the samples. Detailed structural information was carried out by Rietveld refinement, analysis of X-ray data. Microstructure investigation revealed that the grain development of the doped ceramics was controlled by dopant (Zn) ions due to solute drag effect. Impedance spectroscopy was used to investigate the contribution of grains, grain boundaries and electrode interface effect to the dielectric response. Dielectric parameters observed to be improved for higher Zn/Sr ratio in studied compositions. The Ca0.95Sr0.05Cu3Ti3.90Zn0.10O12 ceramic composition shows a colossal dielectric permittivity of similar to 37,788 and loss similar to 0.049, which are stable within a broad frequency region. Reduced tan delta over a broad range of frequency was well ascribed to the highly insulating grain boundaries. The giant dielectric properties of the system were found to be in accordance with Internal Barrier Layer Capacitance (IBLC) model and correlated to their electrically heterogeneous structure. (C) 2018 Elsevier B.V. All rights reserved.