Research On The Low-sintering Behavior Of Microwave Dielectric ZnO-Nb₂O₅-TiO₂ Ceramics

The development of microwave technology is continuously pushing mobile communication equipments and portable terminal to micromation and modularization. Low Temperature Co-fired Ceramic (LTCC) technique is the best method to achieve the aim. To match the LTCC technique and the request of high frequency components, microwave dielectric ceramics are developing to low sintering temperature, high Qf values and lowτf values.ZnNb2O6 ceramic is an excellent microwave dielectric ceramic with high Qf value (83700 GHz). However, it has low relative permittivity(25), large negativeτf value(-56 ppm/℃) and high sintering temperature (1150℃) which stops it from sintering with low melting point electrode materials like Ag, Cu etc. For the above, in order to promote the relative permittivity and adjust theτf value, we added some amount of TiO₂ to the ZnNb2O6 ceramic and found that ZnO-Nb2O5-2TiO₂ ceramics could sinter at 1125℃withεr = 46.79, Qf = 13481 GHz,τf = 57.3 ppm /℃.Then, SnO₂ and MnO₂ was doped to modified the ceramic. The doping of SnO₂ and MnO₂ could inhibit the formation of the second phase, improve the Qf values of the ceramics in a certain range and lower theτf values. Also, MnO₂ could lower the sintering temperature to 1060℃. The results showed that ZnO-Nb2O5-1.92TiO₂-0.08SnO₂ ceramics could sinter at 1125℃withεr = 47.84, Qf = 16533 GHz,τf = 23.4 ppm/℃and ZnO-Nb2O5 -1.91TiO₂-0.08SnO₂-0.01MnO₂ ceramics sintered at 1060℃wthεr = 44.13, Qf = 17050 GHz,τf = 15.7 ppm /℃.At last, we used ZnO-B₂O₃ (1:1) and BaO-CuO-B₂O₃ (1:1:1) two types of glass to lower the sintering temperature, respectively. The result demonstrated that the effect of BaO-CuO-B₂O₃ glass on lowering the sintering temperature of ZnO-Nb2O5 -1.91TiO₂-0.08SnO₂-0.01MnO₂ was much better than ZnO-B₂O₃ glass. With 4 wt.% ZnO-B₂O₃ glass doping, the ceramics could sinter at 930℃withεr = 41.2, Qf = 8120 GHz,τf = -18.9 ppm /℃; with 3 wt.% BaO-CuO-B₂O₃ glass addition, the ceramics could sinter at 860℃withεr = 41.2, Qf = 8120GHz,τf = -18.9 ppm /℃, and had good prospects in LTCC applications.