In this work, we developed a novel system of isovalent Zr
4+ and donor Nb
5+ co-doped CaCu
3Ti
4O
12 (CCTO) ceramics to enhance dielectric response. The influences of Zr
4+ and Nb
5+ co-substituting on the colossal dielectric response and relaxation behavior of the CCTO ceramics fabricated by a conventional solid-phase synthesis method were investigated methodically. Co-doping of Zr
4+ and Nb
5+ ions leads to a significant reduction in grain size for the CCTO ceramics sintered at 1060 °C for 10 h. XRD and Raman results of the CaCu
3Ti
3.8-xZr
xNb
0.2O
12 (CCTZNO) ceramics show a cubic perovskite structure with space group
Im-3. The first principle calculation result exhibits a better thermodynamic stability of the CCTO structure co-doped with Zr
4+ and Nb
5+ ions than that of single-doped with Zr
4+ or Nb
5+ ion. Interestingly, the CCTZNO ceramics exhibit greatly improved dielectric constant (~10
5) at a frequency range of 10
2–10
5 Hz and at a temperature range of 20–210 °C, indicating a giant dielectric response within broader frequency and temperature ranges. The dielectric properties of CCTZNO ceramics were analyzed from the viewpoints of defect-dipole effect and internal barrier layer capacitance (IBLC) model. Accordingly, the immensely enhanced dielectric response is primarily ascribed to the complex defect dipoles associated with oxygen vacancies by co-doping Zr
4+ and Nb
5+ ions into CCTO structure. In addition, the obvious dielectric relaxation behavior has been found in CCTZNO ceramics, and the relaxation process in middle frequency regions is attributed to the grain boundary response confirmed by complex impedance spectroscopy and electric modulus.
相似文献