Dielectric properties of Bi2PbNb2O9 ceramics prepared by different techniques

Different techniques for the synthesis of Bi2PbNb2O9, namely the mixed oxide technique, molten salt synthesis, hydro-thermal synthesis, co-precipitation and the tartaric acid gel method were investigated and the results on the dielectric properties are reported. The heat-treatment of the precursor powders was the same for all precursor powders. Sintering at 1 040 °C under ambient pressure resulted in polycrystalline specimens, while "hot-forging" at 1 040 °C with a pressure of 20 MPa produced c-axis aligned samples. Phase composition and crystallite orientation of the sintered bodies were analyzed by X ray diffraction. Single-phase material was obtained in all cases. "Hot-forging" not only yielded c-axis orientation, but also increased the relative densities above 99.4 %. The relative permittivity decreased for c-axis oriented material compared to polycrystalline ceramics. Values for the relative permittivity for the "hot-forged" specimens at 100 °C at 100 kHz varied between 165 and 250, depending on the fabrication method. The Curie temperature for the c-axis aligned samples was 568 °C, independent of the nature of the precursor powders.