A novel approach to achieve high dielectric permittivity and low loss tangent in CaCu3Ti4O12 ceramics by co-doping with Sm3+ and Mg2+ ions

A novel strategy to improve the dielectric properties of CaCu3Ti4O12 ceramics was proposed by codoping with Sm3+ and Mg2+. Sm3+ substituted in Ca2+ sites can effectively suppress the grain growth, achieving a fine grained ceramic microstructure. Mg2+ was selected to be substituted into Cu2+ sites to enhance the grain boundary (GB) resistivity for reducing the loss tangent (tan delta). High dielectric permittivity epsilon' approximate to 1.25 x 10(4) and low tan delta approximate to 0.039 at 1 kHz were successfully accomplished in a Ca0.925Sm0.05Cu2.70Mg0.30Ti4O12 ceramic. Non-Ohmic properties were also enhanced. A slight increase in Ti3+/Ti4+ ratio in (Sm+ Mg) co-doped CaCu3Ti4O12 ceramics was confirmed by the X-ray absorption near edge structure. Changes in tan delta values for all the co-doped ceramics were very consistent with their variations in GB resistance. The dielectric and non-Ohmic properties of co-doped ceramics were significantly improved by tuning both the geometric and intrinsic factors, i.e., increasing the density of GB layer and enhancing the GB resistance, respectively. (C) 2015 Elsevier Ltd. All rights reserved.