The Synthesis, Structure And Property Of BaTiO₃ Solid Solution By Microwave Irradiation

The research of preparation and properties of barium titanate has been a focal point in the field of inorganic solid chemistry since the excellent dielectric property of BaTiO₃ were discovered in 1940s. As one of the most important function ceramic and basic raw materials, BaTiO₃ has been widely applied in the production of electric components such as high-property ceramic capacitor, multilayer ceramic capacitor, PTC heat-sensitive resistance, resonance implement, medium amplifier, and is indispensable in electronic industry. Its dosage is largest as capacitor material and basic matrix of electric function ceramic at present.But because of the structure of BaTiO₃ molecule, it has some shortcomings. For example, it has the highest dielectric constant at 120 ℃ (～ 10⁴), while its dielectric constant at room temperature is only 1 / 6 of the Curie point, which greatly limited its practical applications. Otherwise, its dielectric loss is large, and its capacity changes greatly with the variety of temperature.It is hypothesized theoretically that the Curie point of BaTiO₃ may be lowered and broadened when the large Ba²⁺ ions are partially replaced by small-sized ions, or inactive Ti⁴⁺ ions are partially replaced by active ions. The preparation of BaTiC?3 powders and ceramic has great effect on the grain size and density of BaTiO₃,which influence the dielectric property of BaTiO₃ strongly. Additionally, the difference between ceramic and single crystal is that there are many crystal boundary in the ceramic, which have important effects on the performance of material. Thus it is needed to adulterate some ions into the powder grain and crystal boundary. At present, solid phase adulteration was adopted in the production process of electric component in industry. The oxides of Sr, Zr and some rare earth elements are adulterated in BaTiO₃ to improve its property, but the solid phase adulteration is not homogeneous and the expected improvements of the parameters for the component can not be achieved. Although a Sol-Gel method for adulterating BaTiO₃ has been reported in recent years, its wide use is limited by the high price of the materials. Except the rapid transfer of microwave energy to thermal energy in polar solution, the penetration property of microwave electromagnetic radiation through solution should result in a uniform heating for the reaction solution, many researchers exercise microwave technique in a lot of chemical fields, and have obtained fruitful success. In succession, synthesising zeolite molecular screen, inorganic...