Study On Microwave Sintering Of Dielectric Ceramics

The technology of microwave sintering is the method which use the special band of microwave to couple the basic fine structure of materials to arising heat, and the dielectric loss of materials make itself heated to the sintering temperature to achieve densification. It is an important technical means that can be used to prepare materials which have high quality or new properties fast. It has many benefits such as lower sintering temperature, shorten sintering time, and improve the energy efficiency and security, etc.In this paper, four 1.5kW microwave sources are added to 6 kW, through optimizing the resonant cavity and the insulation device, we designed an industrial microwave oven. When the input microwave power is 1.5kW, the power density of the furnace cavity 30kW/m3, and when the input microwave power is 6kW, the power density of the furnace cavity has reached 120kW/m3. Deficiency is that the microwave source power only four levels adjustable, so it is difficult to control the rate of rising temperature accurately, and it just only applies to material which have less stringent requirements on the heating rate, Such as the synthesis of ceramic powders, etc.In this paper, the self-designed industrial microwave was used to synthesis K0.5Na0.5NbO3 (abbreviated as KNN) Lead-free piezoelectric ceramic powder. A reasonable insulation device and a microwave heating curve are designed, the influence of different microwave synthesis temperature to the powder properties and microstructure of KNN are studied. The results showed that microwave synthesis can lower the synthesis temperature about 200℃and cut down the processing time to about 1/20, comparing to electric heating method need synthesis temperature above 800℃. The powders obtained by microwave synthesis exhibit fine morphology, uniform granularity and less reunion, microwave synthesis is a kind of good prospects for the development of materials process method.Microwave sintering and electrical-thermal sintering techniques were used to prepare the (Zr0.8Sn0.2)TiO4 (ZST) ceramics whose densification, component, microstructure and dielectric performance were characterized by Archimedes method, X-ray diffraction (XRD), scanning electron microscopy (SEM) and HP8720ES network analyzer, etc. The results show that the microwave sintering method can decrease the sintering temperature about 70℃and the sintering time about 150min and can enhance the densification. The value of sr and Q of ZST increased with the increasing of sintering temperature, and the corresponded value increase 17.5% and 14.3% respectively, compared with electrical-thermal sintering. The densification mechanic and performance were analysised more systematically in theoretically.