Effects Of Rare Earth On ZnO Electrical Ceramics Powders

ZnO powders were prepared by sol-gel method and precipitation method. The preparation parameters for ZnO powders were studied. ZnO conductive powders were penetrated by gaseous penetration of La and Pr in gaseous state. The composition, structure and electric conductivity of ZnO powders were studied.The preparation parameters of ZnO powders by sol-gel method: room temperature, stirring 3h, sintering at 840°C, sintering 1h at 200°C, 2h at 400°C, and 1h at 400°C. The process parameters of precipitation method are: sequential washing, 80 drops/min, sintering at 200°C. ZnO powders prepared by precipitation method are uniform. The grain size is about 100nm, which is smaller than that of ZnO powders prepared by sol-gel method.ZnO conductive powders were prepared by gaseous penetration of La and Pr in gaseous state. Experiment results show that La and Pr can evidently improve the electric conductivity of ZnO powders. When the La content is 2%(wt), the penetration time is 4h, the penetration temperature is 420°C, the resistivity of modified ZnO powders is lowest, which decreased from 10¹⁴Ω·cm to 1.6×10⁶Ω·cm. When the Pr content is 2%(wt), the penetration time is 4h, the penetration temperature is 400°C, the resistivity of modified ZnO powders is lowest, which decreased from 10¹⁴Ω·cm to 1.9×10⁶Ω·cm.XRD analysis show that, after gaseous penetration of La and Pr in gaseous state, the main peaks of ZnO powders did not change, but there are two small peaks at 29.5° and 30.5°, which are relating to La and Pr. It indicated that La and Pr have penetrated into ZnO powders and leaded to the increase in electric conductivity. SEM results show that, after gaseous penetration, grains of the powders are refined evidently and agglomeration behavior is decreased. Thermogravimetric analysis show that ZnO powders penetrated by La has good thermal stability, which has a good application in the future.