Research On Low Temperature Sintering Of High Dielectric Constant Li-Nb-Ti Microwave Dielectric Ceramics

With the rapid development of microwave communication technology, researchers come up with higher require for microwave dielectric ceramics. Especially, the research of low temperature co-fired ceramics(LTCC) has become the hot research direction in this field.Li2O-Nb2O5-Ti O2(LNT) ceramics have excellent microwave dielectric properties: high dielectric constant, high quality factor and temperature coefficient of resonant frequency near to zero. Compare with other microwave dielectric ceramics which have high dielectric constant(The sintering temperatures are above 1300℃ usually), LNT ceramics have lower sintering temperature(1100℃). So it is easyer to achieve the effect of decreasing the sintering temperature through doping with little influence on the microwave dielectric properties for the LNT ceramics. The LNT material is a well developmental potential new functional microwave dielectric material. It represents that the LNT ceramics could be promising for LTCC applications through using additives to decrease the sintering temperature.The paper main includes two part contents which are the optimization of process and decreasing the sintering temperature through using additives for LNT ceramics. In the study of decreasing the sintering temperature through using additives for LNT ceramics, the additives used in our study work were Bi2O3, Li-Al-B, Li-B-Si, V-Cu. In these additives, the Li-B-Si are two additives which are prepared by the different proportions of mole, devoted as S1 and S2 addition respectively. The main study work is below:(1) In the experiment of ball milling time, the investigation showed that with the increasing of ball milling time, the microwave dielectric properties of LNT ceramics could be improved in a certain extent. When the ball milling time was four hours, the best microwave dielectric properties of r? =69.14, ?tg =6.37×10-4, Qf =5900GHz were obtained.(2) In the experiment of ball milling proportions, the investigation showed that with the different proportions of zirconia balls and alcohol in the ball milling proportions, the microwave dielectric properties of LNT ceramics were different. Finally, the best proportion among powders, alcohol and zirconia balls of 1:0.75:6 was obtained, which showed excellent microwave dielectric properties of r? =68.92, tg? =6.33×10-4, Qf =5829GHz.(3) The effect of LAB addition on the microwave dielectric properties of LNT ceramics was investigated. The investigation showed that the LAB addition could decrease the sintering temperature of LNT ceramics in a certain extent. The LNT ceramics sintered at 950℃ with 3% of w(LAB) addition were dense, and the excellent microwave dielectric properties were r? =61.23,Qf=4704GHz,f? =2.2ppm/℃.(4) The effect of VC addition on the microwave dielectric properties of LNT ceramics was investigated. The investigation showed that the VC addition could decrease the sintering temperature of LNT ceramics in a certain extent. The LNT ceramics sintered at 925℃ with 3% of w(VC) addition were dense, and the excellent microwave dielectric properties were r? =61.38,Qf=5420GHz,f? =-3.2ppm/℃.(5) The effect of S1 addition on the microwave dielectric properties of LNT ceramics was investigated. The investigation showed that the low-level doping of S1 addition in LNT ceramics could achieve good effect of decreasing sintering temperature, and it has little influence on the microwave dielectric properties for LNT ceramics. The XRD analysis showed that secondary phase wasn’t observed for the LNT ceramics with S1 addition.The LNT ceramics sintered at 900℃ with 0.75% of w(S1) addition were dense, and the excellent microwave dielectric properties of r? =66.74, ?tg =9.99×10-4, Qf =4347GHz were obtained.(6) The effect of S2 addition on the microwave dielectric properties of LNT ceramics was investigated. The investigation showed that the S2 addition could effectively decrease the sintering temperature of LNT ceramics. The XRD analysis showed that secondary phase wasn’t observed for the LNT ceramics with S2 addition.The LNT ceramics sintered at about 875℃ with 0.75% of w(S2) addition were dense, and the excellent microwave dielectric properties were r? =63.26, tg? =9.19×10-4, Qf =4821GHz.