| BaO-Nd2O3-TiO2 based dielectric materials are critical for high frequency capacitor, microwave resonators and filters for their excellent dielectric properties, and have important applications in communication technology. As the multilayer ceramic capacitors(MLCC) are miniaturized and have lower cost, it is urgent to develop a dielectric material that can be co-fired with base metal electrode in reducing atmosphere. BaO-Nd2O3-TiO2 based ceramics were chosen as the research objective in this article, the influence of sintering aids, acceptor-doping, iron substitution donor and acceptor co-doping and sintering process on composition, crystal structure, micro-structure, dielectric properties and insulation characteristic of BaO-Nd2O3-TiO2 ceramics which were sintered in reducing atmosphere were studied.Ba4.5(Nd0.7Sm0.3)9Ti18O54 ceramic with excellent dielectric properties were be chosen as the basic system. Its sintering temperature can be decreased to 1180? when doped with different low-melting-point powders such as SA1, SA2 and SA3 The dielectric properties were almost the same when samples were sintered in air, the ceramic was semi-conducted when sintered in N2 atmosphere, the insulation resistivity was improved compared with non-doping samples, and samples doped with SA3 had the best properties of ?r=1078.50, tan?=0.076, ?=6.58×10+6??cm.The effect of acceptor CuO(0-1.5%) and MnCO3(0-3%)with different content on the composition and dielectric properties of BNST ceramic doped with SA3 sintered in reducing atmosphere was studied. The XRD result shows that the main phase was BaNd2Ti4O12 with tungsten bronze structure, copper andmanganese completely come into the crystal lattice to replace Ti4+. Also, the ceramic was more compact when doped with CuO and MnCO3. With the increase of acceptor content, the anti-reducing properties of BNST-based ceramic were significantly improved. The acceptor cannot completely compensate the electrons that generate by oxygen vacancy and the dielectric loss of ceramic is high, when the acceptor CuO content is less than 1.5 %. The anti-reducing properties of BNST-based ceramic is excellent with its insulation resistivityreaching to 10+12??cm when the MnCO3 content is more than 1.8%. The ceramic can achieve the best performance of ?r=79.02, tan ?=2.3×10-3, TCC=-65ppm/K, and the insulation resistivity was 1.2×10+12??cm.The paper also studied the effect of Sm3+ and Bi3+ to substitute Nd3+. With the increase of Sm3+ displacement, the dielectric constant decreased and the TCK was closer to zero when the ceramics were sintered in air. The TCK can reach-22ppm/K when the Sm:Nd=5:5. When the Bi2O3 content was less than 0.12, the BNT-based ceramic formed solid solution with single structure of tungsten bronze, With the increase of Bi2O3 content, the ceramic dielectric constant increased to 93.6, the dielectric loss and TCK were decreased.The influence of donor V2O5 content, acceptor MnCO3 and sintering aidsSA3 co-doped to the structure and dielectric properties of Ba4.5(Nd0.7Sm0.3)9Ti18O54 ceramic sintered in different atmosphere was studied. With the increase of the V2O5 content, the ceramic dielectric constant was slightly decreased while the loss was increased when sintered in air. The introduction of V2O5 can significantly improve the dielectric properties of the ceramic, which was sintered in reducing atmosphere. With the increase of the doping content, the dielectric loss was decreased. The ceramic can achieve the best performance of?r=78.1, tan?=2.3×10-4.The study of reducing atmosphere sintering process shows that properly decreasing the sintering temperature, raising the re-oxidation temperature and increasing the O2 content of re-oxidation process properly can improve the dielectric properties of BNST-based ceramic. However, we also need to guarantee that the Ni electrode won't be oxidized when we adjustthe sintering process.By the means of modifying the BaO-Nd2O3-TiO2 based ceramic, this paper developed a high frequency and permittivity ceramic with excellent dielectric properties which can be used in BME MLCC field. The related research results established a good foundation for the application of the anti-reducing properties of BNT-base MLCC. |
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