Highly orientated Mn-doped BaTiO3 thin films have been prepared on Nb-doped SrTiO3 substrate by pulsed laser deposition. Structural and electrical studies indicate that pure and Mn-doped BaTiO3 thin films show single phase character and good ferroelectric performance. All of the Mn-doped BaTiO3 thin films show obvious room-temperature ferromagnetism and the magnetization increases with the growing concentration of doped Mn. A bound magnetic polaron model was proposed to understand the observed ferromagnetic behavior of resistive Mn-doped BaTiO3 thin films. Our results demonstrate that ferromagnetism can be induced in the ferroelectric BaTiO3 film, which makes it a promising single-phase multiferroic.

We prepared La doped of CaCu3Ti4O12 ceramics by a solid-state sintering process and observed nonlinear electrical varistor and high dielectric behaviors. Phase composition analyses show that the La can substitute on the Ca sites completely, and have no influence on the phase composition. The impedance spectroscopy at room temperature indicates that the La doping can maintain the dielectric permittivity of CaCu3Ti4O12 (∼104). The relationships between electrical current density versus applied electrical field show that these ceramic samples exhibit nonlinear varistor characteristics, which should be ascribed to the existing potential barrier height at the grain boundary.

The dielectric and varistor properties of MgTiO3–CaCu3Ti4O12 composite were investigated in term of a new composite with high dielectric permittivity and breakdown voltage. The MgTiO3–CaCu3Ti4O12 composite ceramics were prepared by a traditional solid‐state method. Analysis of microstructure indicated that MgTiO3 addition can refine the grain size. Impedance spectroscopy results showed that the dielectric constant and loss of the composites were stable with the frequency and temperature. The activation energy calculated by the variation of electrical modulus was almost same (0.12 eV) as previously reported one. Especially, the breakdown voltage of the composite ceramics can by adjusted from 200 to 1200 V/mm by controlling the ratio of the amount of CCTO and MgTiO3 composites.

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To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb -and- Co doped ZnO and TiO 2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol–gel methods respectively, and then obtained the TCCTO/ ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of ~210(1 kHz) with a nonlinear coefficient of ~11. The dielectric behavior of TCCTO/ ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.