Advanced Materials Research Vol. 906

Abstract: Ba_0.985Bi_0.01TiO₃-BaTi_1-xZr_xO₃ powders have been synthesized by two-step soft chemical method to satisfy EIA-X8R specification. Microstructural evaluation conducted by X-ray diffraction and scanning electron microscopy confirms the hierarchical structure of the ceramic grain. The shape of the ε-T curves near the dielectric peak becomes broad with the increase of Zr content. The permittivity of Ba_0.985Bi_0.01TiO₃-BaTi_0.9Zr_0.1O₃ ceramic is ~3000, C/C20 °C is-14.67%, 6.23% and-14.50% at-55°C, 130°C and 160°C, respectively, and the dielectric loss is less than 0.020. This work shows that the two-step soft chemical method is a promising approach for high performance temperature-stable capacitor materials.

Abstract: (Bi_1.5Zn_0.5)(Zn_0.5Nb_1.5)O₇ (BZN) ceramic samples were prepared by solid state reaction. B₂O₃ was introduced by liquid coating technology with H₃BO₃ solution in the BZN ceramic specimen to reduce its sintering temperature. The sintering behavior, phase composition and dielectric properties of ceramics were investigated by X-ray diffraction, scanning electron microscopy and vector network analyzer. The (Bi_1.5Zn_0.5)(Zn_0.5Nb_1.5)O₇ ceramic composite could be sintered well at 900°C for 3h when 0.9M/l H₃BO₃ was added and showed good dielectric properties of ε_r=150,Q×f=228,τ_f=-362ppm/°C.

Abstract: Low temperature co-fired ceramics (LTCC) technology becomes crucial in the development of various modules and substrates in electronic packaging, especially in wireless and microwave applications [. With this technology, passive components (such as capacitors and inductors) can be embedded into substrates, and co-fired with high-conductive metals (such as silver and copper) below 900°C. Therefore, the shringkage and dielectric properties of LTCC are of great importance to the performance of components. So far, ceramic/glass composites have been widely researched for LTCC application due to tailored physical properties and low sintering temperature [2-3].

Abstract: The effect of milling time and sintering process on the dielectric properties of BaTiO3-based X9R ceramics was investigated. The characterization of the raw powders and the sintered ceramic was carried out by X-ray diffraction and scanning electron microscopy. The particle size distribution of the mixed powders was examined by Laser Particle Size Analyzer. The results shown that with the milling time extended, the Cruie Peak was depressed, or even disappeared. Moreover, with the rise of sintering temperature, the dielectric constant of the ceramics increased and the dielectric loss decreased gradually. Eventually, by milling for 11h and sintering at 1090°Cfor 2h, good dielectric properties were obtained, which were ε25°C≥ 2526, εr/εr25°C≤± 12% (–55~200°C), tanδ≤1.12% (25°C).

Abstract: Low temperature co-fired ceramics (LTCC) technology becomes crucial in the development of various modules and substrates in electronic packaging, especially in wireless and microwave applications [. self-integrated component has laid basis on flexibility of design, wiring density and dependability for multilayer structures due to LTCC technology. Recently, with the rapid progress in wireless communications,to realize more highly integrated passive components in multilayer LTCC structure, however, it is important to control the matching behavior between component and substrate. The dielectric compositions the permittivity range of which is 20100 are most appropriate for realizing strip or microstrip resonator structures in LTCC multilayer structures due to the RF frequency range which is used in current telecommunication systems (130GHz) and the desirable chip sizes in the current technologies (210 mm)[.

Abstract: The sintering temperature of BaTiO₃ powder was reduced to 950°C due to the Bi₂O₃-LiF-CaF₂ addition.Excellent densification was achieved after sintering at 950°C for 10h. The low sintering temperature of newly developed capacitor materials allows a co-firing with pure silver electrodes.The dielectric constant and the temperature stability of the dielectric constant satisfied the X9R standard, which dielectric properties of were ε_25°C 1115, ΔC/C_25°C±12% (55~200°C), tanδ1.5% (25°C)_.

Abstract: Cu-modified graphitic ordered mesoporous carbon supported TiO₂ catalyst was synthesized based on a hard template method. X-ray diffraction, nitrogen adsorption-desorption, scanning electron microscopy and transmission electron microscopy analysis techinques were used to characterize the sample. It was observed that copper and anatase TiO₂ nanoparticles were well dispersed in the Cu-modified mesoporous graphitic carbon, and the resulting composite with ordered mesostructure and high specific surface area exhibited an exceptionally high activity in the photocatalytic reduction of CO₂ with H₂O under simulated solar irradiation.

Abstract: Titanium-based composites with bioactive phases were produced with TiH₂ and 10% in volume of calcium phosphate. The mixtures were prepared either by conventional powder metallurgy processing or by ultrasound, dried in a rotary evaporator, pressed at 600 MPa and vacuum-sintered at 1200 °C for 2 hours. Crystal phases of the as-fabricated composites are found to be α-Ti, CaTiO₃ and Ti_xP_y phase (s). The Ti_xP_y and CaTiO₃ phases resulted from the reaction between titanium and tricalcium phosphate at about 1130 °C. Calcium phosphate was better dispersed by ultrasound leading to a higher compressive strength of the composite and a more uniform Ca-P deposition in simulated body fluid solution.

Abstract: In order to resolve environmental and sustainable energy concerns, significant efforts are required to find ways to minimise the use of fossil fuels and to shift to renewable energy resources such as solar, wind, and geothermal power generation. The key to success lies in developing reliable large scale high power energy storage devices. The lithiumair battery has been suggested as one candidate because of its exceptionally high energy storage capacity. Non-aqueous metal-air batteries utilising alkali and alkaline earth metal anodes also offer great gains in energy density over the state-of-the-art Li-ion battery. They are also unique power sources because the cathode active material (oxygen) does not have to be stored in the battery but can be accessed from the atmosphere. Moreover, alkali and alkaline earth elements are much more abundant than lithium and therefore would offer a more sustainable energy storage solution for even beyond the long-term. This work is to enable the uptake of this technology by fully analysing its principle and by exploring the application of nanostructured catalytic cathode materials. The potential of alkali and alkaline earth metal-air batteries will be demonstrated by their electrochemical cycling performance and will be compared with the lithium-air battery. The challenging issues will be discussed according to experimental observations.