Papers by Keyword: BaTi₄O₉

Abstract: To promote the application of BaTi₄O₉ in higher-end fields, BaTi₄O₉ precursor has been prepared with sol-gel method (SGM. The objective products have been obtained at different temperatures and SSR-BaTi₄O₉ samples has been prepared for compare experiments. The studies of thermal analysis, XRD analysis, TEM analysis, specific surface area analysis, DRS analysis and FS analysis show: the crystalline of the product obtained by SGM is more purity than the product obtained by SSR; The SGM600 sample is amorphous, which can be used as an optical catalyst because of the maximum specific surface area; The SGM1000 sample is the most pure, uniform and complete in crystal.

Abstract: The BaTi₄O₉ submicron powders were synthesized by a sol-gel method, and the sintering behavior and microwave dielectric properties of BaTi₄O₉ ceramics prepared from powders with different particle sizes were also investigated. The particle size of powders calcined at 700 °C, 800 °C, 900 °C and 1000 °C were 8-10 nm, 70-90 nm, 100-120 nm and 140-170 nm, respectively. The 70-170 nm powders benefited the sintering process and microwave dielectric properties, whereas nanoparticles with the size of 8-10 nm damaged the sintering behavior due to the more amorphous phases and lower green density introduced by the large surface area. Sintered at 1175 °C, the BaTi₄O₉ ceramic prepared from 100-120 nm size nanoparticles had compact structure and exhibited good microwave dielectric properties of εr = 36.91 and Q×f = 29,833 GHz.

Abstract: Both BaTi₄O₉ and Ba₂Ti₉O₂₀ have the best microwave properties among many compounds in BaO-TiO₂ system. The microwave performance of the ceramics in BaO-TiO₂ system, which were prepared by conventional solid state method, was investigated in this paper. The study indicates that the (Ti,Zr)/Ba ratio has a great effect on the dielectric properties of the ceramic due to different BaTi₄O₉/Ba₂Ti₉O₂₀ ratio. The pure BaTi₄O₉ ceramic exhibits the most outstanding microwave properties, with ε_r=35.55 and Q×f=43300GHz. On the contrary, the dielectric property of the pure Ba₂Ti₉O₂₀ ceramic was not good enough, which should be doped with some additive additions. WO₃ was incorporated into the system and the sintering temperature was adjusted to improve the microwave dielectric property. The Q×f was increased to 38000GHz by adding 1.35mol% WO₃ due to the formation of a little BaWO₄ phase. When sintered at a higher temperature (1380°C), the BaO-TiO₂ system ceramic has ε_r =37.04 and Q×f =44874GHz.

Abstract: In this study we report sintering behavior and microstructures of glass-added BaTi₄O₉ microwave dielectric ceramics with copper paste in reducing atmosphere. Experimental results show a buffer layer may form at the interface of Cu-electrode and BaTi₄O₉ microwave dielectric ceramics if the glass did not diffuse smoothly during sintering, and therefore materials exhibited different colors. X-ray results indicate that Cu reacted with Ba seriously to form complicated reaction products, and some BaTi₄O₉ transformed to barium titanate with various ration of Ba/Ti, which may degrade the dielectric properties of materials.

Abstract: Ba2Ti9O20 (B2T9) and BaTi4O9 (BT4) ceramics have been fabricated using sol-gel technique. The sol-gel derived powder was produced from barium acetate and butyl titanate using acetic acid as solvent. The as-prepared powders were then calcined at different temperatures ranging from 600° to 1200°C. After that, the powder was pressed into pellets and further sintered at different temperatures ranging from 1250°C to 1380°C. XRD characterization and Raman spectroscopy showed that after calcining the sol-gel powder at 900°C for 2 h and sintering the pressed pellets at 1330°C for 4 h, triclinic B2T9 and orthorhombic BT4 ceramics could be obtained. The dielectric constant and Q-value are 35 and 1910 at 6.1 GHz.