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沉淀剂对ZnO压敏陶瓷缺陷结构和电气性能的影响
The effects of precipitant on the defect structures and properties of ZnO varistor ceramics
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摘要: 研究了不同沉淀剂(NH4HCO3和NaOH)对共沉淀法制备的ZnO压敏陶瓷性能的影响。结果表明：不同的沉淀剂对ZnO压敏陶瓷的微观结构及电气性能有明显的影响。其中陶瓷微观结构的变化主要由沉淀剂本身的性质引起；而电气性能的改变除了与微观结构相关外，主要受不同沉淀剂对陶瓷晶界势垒参数的影响；此外，沉淀剂NaOH引入的Na+作为施主杂质离子掺杂ZnO压敏陶瓷，增加晶粒中的自由电子浓度，因此本征缺陷(锌填隙和氧空位)浓度受到抑制，而锌填隙浓度相对于氧空位而言对施主离子掺杂更为敏感。由此，采用共沉淀法制备ZnO压敏陶瓷粉体时，沉淀剂种类的选择很重要，即使微量的杂质也会引起压敏陶瓷性能的较大改变，应尽可能避免杂质离子的引入。Abstract: The effects of different precipitants (NH4HCO3 and NaOH) on the performances of ZnO varistor ceramics which were prepared by coprecipitation method were analyzed. There are noticeable influences for different precipitants to the microstructure and electrical performances of ZnO varistor ceramics. The change of microstructure is caused by the properties of precipitants themselves while the change of electrical performance is caused by the influence of precipitants to the grain boundary potential barrier properties. Besides, the donor impurity ion Na+introduced by NaOH in the ZnO varistor ceramic will increase the free electron concentration in the grain. So the densities of intrinsic defects (zinc interstitial and oxygen vacancy) are restrained. The density of zinc interstitial is more sensitive to donor impurity ions compared with oxygen vacancy. Therefore the choice of precipitant is important when using coprecipitation method to prepare the powder of ZnO varistor ceramics. Even little impurity ions will result in the obvious change of the performance of varistor ceramics. The impurity ions should be avoided in the powder of ZnO varistor ceramics.
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