| In order to obtain microwave ceramic materials sintered at low temperature, Ba6-3x（Nd1-yBiy）8+2xTi18O54 （x=2/3, 0≤y≤1） （BNTB） system ceramics were selected in this dissertation, sintering aids were added to reduce the sintering temperature of BNTB system ceramics. The effects of A-site ions substitution, sintering aids and process conditions on the phase composition, microstructure and dielectric properties of BNTB system ceramics were studied. The main research contents and results are as follows:1. Bi2O3 was added to BNT system, the microstructure and dielectric properties of Ba6-3x（Nd1-yBiy）8+2xTi18O54（x=2/3） were studied, the relationship between them were also studied. It was found that the dielectric constant and dielectric loss of the specimens increased when y value increased. When y value increased, the TCC value at -55℃moved toward the negative direction, but the TCC value at 125℃had the opposite trend. It has been reported that the solid solubility of Bi3+ in Ba6-3x（Nd1-yBiy）8+2xTi18O54 （x=2/3） is about 0.15, when the y value was greater than 0.15, the second phase Bi4Ti3O12 which having high dielectric constant appeared, the appearance of this second phase could increase the dielectric constant of the system. When the y value was less than 0.15, there was no second phase. Bi3+ which has similar ion radius with Nd3+ will substitute for part of Nd3+ or occupy vacant A2 sites which have larger space, so Bi2O3 doped BNT system change to full-filled tungsten bronze-like structure. Furthermore, the cell volume and the spontaneous polarization of Ti4+ ions increased with the content of Bi2O3. So the dielectric constant shows linear increase with the content of Bi2O3. The dielectric loss increased mainly due to the strengthened polarization consumed more energy.2. GB glass was added to BNTB system to decrease the sintering temperature of the system. When the concentration of GB glass was 10%, the sintering temperature of the BNBT system could be lowered to 910℃. When GB glass which has low melting point were added, liquid phase wetted grains in the sintering process, this can promote mass diffusion, so the sintering ability was effectively promoted and the sintering temperature wad effectively decreased.3. Microwave dielectric ceramic materials which have excellent dielectric properties were obtained in the experiments. The dielectric parameters are listed below:≈77, tg =0.7 10-4（f=1MHz） c=±20ppm/℃（Bi2O3 as additive）sintered at 1200℃。≈80, tg =1.0×10-4（f=1MHz） c=±15ppm/℃（Bi2O3 as additive）sintered at 1200℃。≈87, tg =1.3 10-4（f=1MHz） c=±30ppm/℃（Bi2O3 as additive）sintered at 1200℃。≈54, tg =2.3 10-4（f=1MHz） c=±20ppm/℃（GB glass as additive）sintered at 910℃。... |
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