Xiuli Chen

Dc-bias-field-induced Dielectric Relaxation and AC Conduction in CaCu3Ti4O12 Ceramics

The dielectric relaxation and ac conduction of CaCu3Ti4O12 (CCTO) ceramics were investigated at different temperatures under a dc bias. The dc bias gives rise to space charge accumulation, i.e. an electrode response, resulting in the significant increase of dielectric permittivity and dielectric loss tangent. Two Debye-like relaxations, arising from electrode and grain boundary responses, are present at low frequency with an increase of the dc bias. The electrode and grain boundary relaxations are distinguished according to the impedance spectroscopy and the frequency-dependent ac conductivity. The relaxation times of electrode and grain boundary relaxation are 0.955 ms and 0.026 ms, respectively, with a dc bias of 10 V at 328 K.

Low-temperature synthesis of (Pb,La)(Zr,Ti)O3 thick film on Ti substrates by the hydrothermal method using oxide precursors

We simplified the hydrothermal process using oxides instead of liquid-base reactants as precursors. Lead lanthanum zirconate titanate Pb0.94La0.06(Zr0.65Ti0.35)0.985O3 (PLZT) thick films were prepared on Ti substrates at 150°C via hydrothermal synthesis. The films with a single perovskite structure were smooth and the surfaces were free of micrometer scale cracks. The thickness of the film was about 56μm. The dielectric constant and dielectric loss were 665 and 0.03, respectively, at 1MHz. Even at high frequencies the dielectric properties of the PLZT film still remain stable. The samples showed excellent reproducibility in the measurement of leakage current.

SYNTHESIS OF Pb(Mg1/3Nb2/3)O3–PbTiO3 FILM ON Ti SUBSTRATES BY A SINGLE STEP AT LOW TEMPERATURE

The relaxor ferroelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 compositions are of interest owing to their excellent dielectric, electromechanical, electro-optical, and other properties. In this paper, the 0.80Pb(Mg1/3Nb2/3)O3–0.20PbTiO3 (PMN–PT 80/20) films with pure perovskite structure were synthesized by a single step at 150°C. The corresponding oxides were used as starting materials, namely PbO, MgO, Nb2O5, and TiO2. By using oxides as precursors, we simplified the hydrothermal process, allowing the process to be more economical. The influences of the Ti metal substrate on the PMN–PT 80/20 films are investigated. By surveying the variations of films, it was suggested that the substrate reacted with the ions in the solution. The films were smooth and homogeneous. There were no cracks and abnormity crystals on the surface of the films. The thickness was about 20 μm. The frequencies dependence of the dielectric properties of PMN–PT 80/20 films was stable even at a high frequency range over 1 MHz.