Papers by Author: Yu Shuang Zhao

Abstract: Fine grained and dense dielectric ceramics of the BaO-Nd2O3-TiO2 system have been fabricated by the most advanced Spark Plasma Sintering (SPS) technology, whose average grain size is about 100nm as determined by SEM. XRD showed that the diffractive peak of the sample was broadened clearly. The nano-ceramic microstructure formed by SPS is due to the high pressure up to 50 MPa, low temperature (1000°C) and fast sintering (1 minute). The BaO-Nd2O3-TiO2 ternary nanoceramic sample, which consists of the main phase Nd2Ti2O7 with perovskite-like layer structure (PLS) and the secondary phase BaNd2Ti4O12（Ba4.5Nd9Ti18O54）with perovskite-like tungsten bronze structure, was prepared for the first time by rapidly sintering nano-particles of the xBaO×(0.35-x)Nd2O3×0.65TiO2 compound. Those two phases are formed in BaO-Nd2O3-TiO2 micron-grained ceramics prepared by normal sintering of the nano-particles at 1300°C, resulting in good dielectric characteristics for microwave ceramics; however, dielectric characteristics are significantly degraded in the SPS-sintered samples probably due to the carbon contamination from the graphite SPS dies.

Abstract: By means of 34.5 GHz millimeter-wave (MMW) sintering, BaO-Nd2O3-TiO2 microwave ceramic dielectric was prepared from nano-particles of the xBaO×(0.35-x)Nd2O3×0.65TiO2 ternary compound, which possess fine grain, low porosity and good dielectric characteristics. The materials which have ultra-low dielectric loss can be fired by MMW heating at very high frequency, which is unable to be done by normal microwave heating at 2.45 GHz. The sintering temperature is 160 ~ 400°C lower than that of normal firing. The ceramic sample consists of the main phase of Nd2Ti2O7 with perovskite-like layer structure (PLS) and the secondary phase of BaNd2Ti4O12 (Ba4.5Nd9Ti18O54)with perovskite-like tungsten bronze structure, being the same as the results from normal sintering. The excellent microwave characteristics were observed.