Effects of Zr doping on the microstructures and dielectric properties of CaCu3Ti4O12 ceramics

► CaCu3Ti3.95Zr0.05O12 (CCTZO) ceramics prepared by a sol–gel method have no impurity phase. ► The CCTZO ceramic exhibits an uniform grain size distribution of about 3–5μm. ► The CCTZO ceramics performs a lower dielectric loss at high frequency ranges. ► The CCTZO ceramics have a broadband stability of the dielectric constant. Zr-doped CaCu3Ti3.95Zr0.05O12 (CCTZO) ceramics were prepared by sol–gel method, and pure-phased structures were observed by the X-ray diffraction. The microstructures and dielectric properties of CaCu3Ti4O12 (CCTO) and CCTZO ceramics were investigated. The CCTZO ceramics possessed a fine-grained microstructure with grain sizes of about 3–5μm, and the grain size uniformity of CCTZO ceramics were enhanced via doping Zr in CCTO ceramics. Meanwhile, CCTZO ceramics exhibited a broadband stability of the dielectric constant and a lower dielectric loss at high frequency ranges. The dielectric relaxation mechanisms of CCTO and CCTZO ceramics were analyzed using the mixed-valent structures. The impedance analysis suggested CCTO and CCTZO ceramics consisted of semiconducting grains and insulating grain boundaries.