The Dielectric Study Of Y₂O₃and NaNbO₃Doped BaTiO₃-based Ceramics

Barium titanate ceramies, which have been developed over the last decades, are a kind of new functional ceramies. It is well known that the barium titanate(BaTiO3) is a ferroelectric and relaxor material with a perovskite structure. It was largely studied because of its electric properties:ferroelectricity, piezoelectricity, positive temperature coefficient, ect. For its dielectric largely depended on temperature, BaTiO3is doped with small amounts of impurities to modify its properties to widen the fields of potential application.The polycrystalline ceramic samples of0.1%Y2O3—Ba(ZrxTi1-x)03, BaTiO3and xNaNbO3(1-x)BaTiO3were prepared by conventional solide-state synthesis technique. The phase constitutions were checkde by XRD and the microstructures were examinded by SEM in room temperture. The dielectiric properties were determined as function of frequency in the temperature range-40-140℃and then it could gain chemical formula and the best sintering temperature.Specimens of0.1%Y2O3—Ba(ZrxTi1-x)O3were labeled as Y-BZT. All the results indicated that they could be indicated with only one perovskite typephase and the regular increase of the lattice constant for rising Zr/Ti. Good dielectric properties with low losses were found without dependence of the frequency and temperature. High permittivity about1000at the room temperature, and Curie temperature140℃were found in the BaTiO3doped a little of Yttrium. By incresing the Zr addition, a shift of Curie temperature towardes lower values and the dielectric constant decreases.Specimens of xNaNbO3—(1-x)BaTiO3were labeled as NN-BT. All the results indicated that NN and BT were detected as solid solution. For x<0.3%or0.45%<x=0.6%, a fairly homogenous distribution and highly densed cremics were founded. The dielectric constant varied below5000, where the dielectric loss was below0.02at1kHz with the good temperture and frequency stability, when0.3%<x<0.45%, the lattice was non-uniform distribution with the semiconducting grain and the insulating gain boundary. The dielectric constant was up to3×105with the dielectric loss was 0.15at1kHz at the room temperature. The dielectric behaviour was belong to diffuse phase transitions and all more relaxor with y larger than2. The best sample was x=0.4%in the sintered temperture1270℃.