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Abstract: The effect of Yb/Mg co-doping on the microstructure and electrical properties of BaTiO3 ceramics sintered under oxidizing, reducing and annealed conditions was investigated. XRD analyses indicated the suppression of the solubilities of the acceptor ions in BaTiO3 under the reducing and annealed conditions. DSC measurements indicated that addition of too much Yb would cause the collapse of the core-shell structure in the BaTiO3 ceramics. The effect of sintering atmospheres on the microstructure and dielectric properties was attributed to the change of the solubilities of the acceptor ions in this core-shell-structured material. [Copyright &y& Elsevier]

High performance X7R dielectric materials were prepared by doping Nb2O5–Co3O4 nanometer composite oxide to BaTiO3 powders, with a dielectric constant as high as 5200 and dielectric loss lower than 1.0%, when they were sintered at 1300 for 2 h. The effect of Nb2O5–Co3O4 nanometer composite oxide was discussed. It was concluded that Nb5+, Co3+ were easier to incorporate into BaTiO3 lattice by using Nb2O5–Co3O4 nanometer composite oxide as dopants than by doping Nb2O5, Co3O4 separately. It was favorable by nanometer oxides doping to make the system hold high dielectric constant and still satisfy the requirement of EIA X7R specification, attributed to the uniform distribution of nanometer dopants in BaTiO3 grain boundaries and the formation of abundant “core–shell” structure with relatively thinner grain shell. [Copyright &y& Elsevier]

Abstract: The influence of Nb on the microstructure and dielectric properties, including temperature dependence of permittivity, dielectric loss, and Curie temperature, has been investigated on Ni-doped BaTiO3 ceramics. Experiments reveal that incorporation of a proper content of Nb in Ni-doped BaTiO3 can control the grain growth, reduce the dielectric loss, shift the Curie temperature to higher temperatures and significantly improve temperature characteristics of the BaTiO3 ceramics. As a result, a novel X8R material is developed in the system, which is very promising for practical use in X8R multi-layer ceramic capacitors (MLCCs). [Copyright &y& Elsevier]

Abstract: The BaNd2Ti4O12 (BNT) solid solution containing composite additives Ba–Zn–B (BZB) were prepared as a low-temperature co-fired ceramics (LTCC). The 20wt.% addition of BZB to BNT significantly lowered the sintering temperature from 1450°C to 900°C without secondary phase formation. The sintering properties of the low-temperature sintered BNT with additives were investigated using dilatometer, scanning electron microscopy (SEM). Liquid phase was formed in the highly doped ceramics. Energy dispersive X-ray spectrometer (EDS) results further confirmed that the material was single phase which is consistent with the X-ray diffractometer (XRD) results. The specimen doped with 20wt.% BZB sintered at 900°C for 0.5h shows excellent dielectric properties: Q×f =3234GHz, ε r =63.2 and τ f =−10.9ppm/°C. [Copyright &y& Elsevier]

Abstract: For the purpose of sintering 0.67ZrTi2O6–0.33ZnNb2O6 ceramics in air, y(y =0.0–2.0) wt% MnCO3 was doped into it by solid-state reaction. XRD analysis suggested there were two phases: the solid solution ZrTi2O6 and the rutile TiO2. SEM analysis demonstrated MnCO3 could promote the grain growth obviously. The addition of MnCO3 had a great positive influence on the Q×f values, for example the sample with 0.7wt% MnCO3 had the highest Q × f value=44,800GHz, which was fifteen times higher than that of the undoped sample, because Mn ions worked as acceptors to receive the unwanted electrons left by the lost oxygen. The dielectric ceramics with the composition 0.67ZrTi2O6–0.33ZnNb2O6 +0.7wt% MnCO3 were sintered well at 1270°C in air and it showed good microwave dielectric properties: εr =44.4, Q × f =44,800GHz and τf =−6.8ppm/°C. Therefore, this method has the advantage over sintering ZrTi2O6–ZnNb2O6 ceramics in oxygen. [Copyright &y& Elsevier]

Abstract: The microwave dielectric properties of (1−x)BaTi4O9–xBaZn2Ti4O11 ceramics were investigated by solid-state reaction technique for obtaining high-Q dielectric ceramics in BaO–ZnO–TiO2 system. And they were strongly determined by the chemical composition. As x was increased from 0.05 to 0.50, BaZn2Ti4O11 phase formed more and more. Therefore, the εr decreased from 37.3 to 32.8 and the Q×f values first raised from 45,300GHz to 60,600GHz (x=0.30) and then started to decline to 58,700GHz (x=0.40), and the τf values varied gradually from 12ppm/°C to −13ppm/°C. 0.7BaTi4O9–0.3BaZn2Ti4O11 ceramics sintered at 1240°C for 3h had excellent comprehensive microwave dielectric properties: εr =34.2, Q×f=60,600GHz and τf =−2ppm/°C. [Copyright &y& Elsevier]