Characterization Of Modified Sol-Gel Derived XSrO·(1-x)BaO·yNb₂O₅·(1-y)TiO₂ Composite Ceramics

Strontium barium niobate with tetragonal tungsten bronze structure and barium strontium titanate with perovskite structure have attracted lots of attention due to their outstanding dielectrical properties and potential applications. However SBN with defect that was difficult sintered to a high density and can abnormal grain grow. So the composite material with good dielectric properties, mechanical properties may be obtained by a composite of BST and SBN. In this paper (1-x)BaO·xSrO·(1-y)TiO2·yNb2O5(BSTN in short) with coexistence of the perovskite and tungsten bronze phases were successfully prepared by a modified sol-gel method, and the formation mechanism of the composite ceramics was investigated in details. The effect of different Sr/Ba ratio and Ni/Ti ratio to the structure and properties of the materials were also studied. Some instruments were chose included X-ray diffraction (XRD), scanning electron microscope (SEM), impedance instrument and also LCR digital bridge.Following results can be obtained from the paper: (1) Compare to the traditional solid method, this modified sol-gel can shorten the sintering time and lower the crystallizing temperature while with a good combination of the two phase without any abnormal grain growth; (2) The presintering temperature was chosen at 800℃through thermal analysis and a heating cure was made; (3) By analysis the sintering mechanism can got that the formation temperature of SBN is higher than that of BST, and the composite ceramics sintering temperature was determined at 1250℃for 3h; (4) BST and SBN can be coexisted in the system well with the x value in range of 0.25~0.75. With the increasing of x value, dielectric constant became lower while the dielectric loss increase. So, the composite ceramic with x=0.3 possess higher dielectric constant and lower dielectric loss means more to improve the dielectrical device; (5) In 0.7BaO·0.3SrO·(1-y)TiO2·yNb2O5 system, with the increasing of y value the material perform a better dielectric property, especially when y=0.7. So, the dielectric properties of composite ceramic were improved largely.