Ceramics-Silikáty 54, (2) 108 - 115 (2010)

Three series of polycrystalline ceramics with a compositional formula of Ba_6-3xLn_8+2xTi₁₈O₅₄ with Ln (lanthanide) = Sm, Gd and Nd and x = 0.0 – 0.7 were synthesized by the standard double sintering ceramic technique. The changes of sintering time ranging from 2 h to 6 h in steps of 1h were taken into consideration showing its effect on the behavior of the ceramics. X-Ray Diffraction analysis confirmed that the crystal symmetry was same i.e., orthorhombic with a possible space group of Pbam, for all the ceramics of the three series. The lattice parameters increased with increased sintering time. Grain morphology was investigated with the help of Scanning Electron microscopy. Fired densities have been observed to be greatly improved with the raised sintering time. There was a considerable and similar effect on dielectric and conductivity properties, for all the ceramics series, carried out at a frequency of 3.0 GHz at room temperature. Dielectric constants were increased up to the sintering time of 4 h and then tended to saturate for raised sintering time in all series. Moreover, the loss tangent was seen to be decreased remarkably with increased sintering time in all the series. Relationship between density, crystallites size and dielectric properties has been presented.