液相对ZnO陶瓷放电等离子体烧结过程的影响

Effect of Liquid Phase on the Spark Plasma Sintering Process of ZnO Ceramic

采用放电等离子体烧结技术制备了ZnO陶瓷,主要研究了液相(醋酸溶液)的添加对烧结过程的影响。结果表明,通过对初始粉料添加约10%的2 mol/L的醋酸溶液,在等离子体烧结过程中,ZnO陶瓷试样在52℃开始收缩,115℃开始致密化,160℃致密度可达95%以上,200℃即可完成致密化。在250℃烧结5 min后,晶粒尺寸从初始粉体的200 nm增长到600 nm。X射线衍射结果表明,在液相辅助等离子烧结过程中,ZnO陶瓷中未出现明显杂相,并且晶粒生长表现出沿外施压力垂直的方向取向生长。通过计算发现,液相辅助等离子体烧结ZnO陶瓷其晶粒生长活化能仅为78.8 kJ/mol,约为传统高温烧结的1/3。ZnO陶瓷试样的室温阻抗测试结果表明,晶界阻抗随烧结温度的升高而下降,从120℃烧结试样的9.82×10^(6)Ω下降到250℃烧结试样的2.75×10^(3)Ω。

ZnO ceramics were fabricated via spark plasma sintering(SPS)technology.The effectof acetic acid solution on the SPS was mainly investigated.The results indicatethat withadding about 10wt%liquid phase(2 mol/L acetic acid solution)during SPS,the shrinkage and densification of ZnO ceramic samples areactivated at 52and 115℃,respectively.The relative density of ZnO ceramic samples can reachthe value of more than 95%and then the samples are fully densifiedwhen the sintering temperature further increasesto 160 and 200℃.The grain grows from 200 nm of the raw particle to 600 nm after sintering at 250℃ for 5 min.The X-ray diffraction results show that no obvious impurity phase can be observed,and the grain growth presentsa clear anisotropic orientation,preferentially growing along the vertical direction of applied pressure.With assistance of liquid phase in SPS,the grain growth activation energy was determined at only 78.8 kJ/mol,a third as large as that sintered in the conventional SPS.Impedance of ZnO ceramic samples was measured at room temperature.It isfound that the grain boundary resistance decreases from 9.82×10^(6)Ωto 2.75×10^(3)Ωwith the increasing sintering temperature from 120 ℃ to 250℃.