Papers by Author: Wei Li

Abstract: The plagioclase feldspar (NaxCa1-xAl2-xSi2+xO8, 0<x<0.67), has been synthesized under sub-solidus conditions using the solid-reaction technique. X-ray diffraction (XRD) was used to study the temperature dependency of the phase and structure transformations. Scanning electron microscopy (SEM) was performed to demonstrate the micro-structure of the sintered samples. The dielectric properties in microwave (MW) frequency region, including the dielectric constant, Qxf and the temperature coefficient were measured by the microwave network analyzer. The results revealed the value of Qxf decreases when 0≤x≤0.2, while increases when 0.2≤x≤0.67. The lowest value of Qxf was at x = 0.2.

Abstract: In this work hexagonal perovskite powders of CaLa4Ti4O15 were prepared by citrate sol-gel method. The calcined temperature was 1150oC, which is lower than that of the conventional solid method. Dense CLT ceramics were produced at sintering temperature of 1600oC. The crystal structures and microstructures were investigated by XRD, TEM and SEM, respectively. Compared with samples produced by solid method, the sol-gel derived CLT ceramics exhibited a near zero temperature coefficient of resonant frequency (τf ) of -6 ppm/oC, and other microwave properties , εr ~ 43, Q×f ~ 42000 GHz were also obtained. Moreover, the sintering temperature of the CLT ceramics could be reduced to 1400 oC by addition of B2O3-ZnO.