Dielectric and nonlinear current–voltage characteristics of rare–earth doped CaCu3Ti4O12 ceramics

Abstract

were prepared by the traditional solid-state reaction method in order to investigate the effect of RE oxide dopants on the electrical properties as a varistor. The phase identification and morphology of the ceramics were investigated by x-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. A high voltage measuring unit and precision impedance analyzer were used to determine the nonohmic (J-E) behaviors and measure the dielectric properties and impedance spectroscopy of the ceramics, respectively. The results showed that RE oxides enhanced greatly the breakdown electric flied but reduced the nonlinear coefficient and the mean grain size of CCTO ceramics. There was a good linear relationship between ln J and E 1/2 , which demonstrated that the Schottky barrier should exist at the grain boundary. A double Schottky barrier model composed of a depletion layer and a negative charge sheet was proposed, analogous to the barrier model for ZnO varistors. The depletion layer width determined by diffusion distance of RE ions and the effective surface states played important roles on the electrical properties of the ceramics.

Modified giant dielectric properties of samarium doped CaCu3Ti4O12 ceramics

“…The decrease in e 0 is associated with the decrease in the grain size. This result observed in Sm-doped CCTO ceramics is similar to those observed in literature for other Ln-doped CCTO ceramics [18][19][20][21][22][23][24][25][26]. This observation can be well ascribed based on the internal barrier layer capacitor (IBLC) model [28],…”

“…The decrease in grain size of Ca 1À3x/2 Sm x Cu 3 Ti 4 O 12 ceramics is therefore due to a reduced GB mobility (or GB diffusion coefficient). It was also found that substitutions of La 3+ , Gd 3+ , Nd 3+ , and Eu 3+ for Ca 2+ in CCTO ceramics can cause a large decrease in the mean grain size [18,20,22,23,26]. The large decrease in grain size of Ca 1À3x/ 2 Sm x Cu 3 Ti 4 O 12 ceramics may be related to the solute drag mechanism, which is an important approach for reducing the GB mobility [29].…”

“…The large decrease in grain size of Ca 1À3x/ 2 Sm x Cu 3 Ti 4 O 12 ceramics may be related to the solute drag mechanism, which is an important approach for reducing the GB mobility [29]. Segregation of some Sm 3+ and other Ln 3+ doping ions at the GBs can produce a dragging effect on the motion of GB [23]. Furthermore, the reduced GB mobility may be due to the fact that the segregation of the additive can change the structure and composition of surfaces and interfaces, resulting in changes in GB and surface diffusion coefficients.…”

“…The dielectric properties of Ln-doped CCTO ceramics have been widely investigated, where Ln is lanthanide metal ions such as La 3+ [18][19][20][21][22][23], Y 3+ [22,23], Gd 3+ [22][23][24], Eu 3+ [23,25], and Nd 3+ [26]. All of these doping ions have an influence on the microstructure and dielectric properties as well as the nonlinear current-voltage behavior of CCTO ceramics.…”

Extremely Enhanced Nonlinear Current–Voltage Properties of Tb‐Doped CaCu3Ti4O12 Ceramics

“…Ceramic composite, CaCu 3 Ti 4 O 12 (CCTO) is one of the most interesting and widely investigated electroceramic materials . This is because it can exhibit a variety important properties which are required for the development of microelectronics.…”