氧离子导体La_(1.9)Y_(0.1)Mo_2O_9细晶粒陶瓷的制备和电学性质研究

Synthesis and electrical property of oxide ionic conductor La_(1.9)Y_(0.1)Mo_2O_9 fine grain ceramic

采用溶胶凝胶法合成的La1.9Y0.1Mo2O9纳米晶粉体,结合微波烧结技术制备出不同晶粒度的La1.9Y0.1Mo2O9块体样品.利用X射线衍射仪(XRD)、高分辨透射显微镜(HRTEM)、场扫描显微镜(SEM)对粉体及陶瓷块体的物相、形貌进行了表征,利用交流阻抗谱仪测试了样品不同温度下的电导率.实验结果表明,掺Y的La1.9Y0.1Mo2O9能将高温立方β相稳定到室温;块体样品致密均匀,平均晶粒度范围在60nm—4μm之间;致密度高的样品表现出高的电导率,其中900℃烧结样品的电导率600℃时高达0.026S/cm,比固相反应法制备的La1.9Y0.1Mo2O9样品高出约1倍.总结认为样品的致密性对电导率影响较大,是通过影响晶界电导率来影响总电导率的,样品的晶粒度(在60nm—4μm范围内)对电导率的影响还不能确定.

A series of La1.9Y0.1Mo2O9 bulk samples of different grain sizes were made by microwave sintering the nanocrystalline powders prepared by sol-gel methods. Phases, microstructure, grain size of the powders and bulk samples were examined by using X-ray diffraction （XRD）, high-resolution transmission electron microscope （HRTEM） and scanning electron microscope （SEM）; and the electrical properties of the bulk samples were studied by AC impedance spectroscopy. Experimental results show that the substituent Y can stabilize the cubic β phase to room temperature; the bulk samples are dense and uniform with an average grain size from 60 nm to 4 μm; the highly dense bulk samples show enhanced ionic conduction, e.g. the conductivity of the sample with relative density 99% is 0.026 S/cm at 600 ℃, which is two times higher than that of bulk samples prepared by solid-state reaction. It can be concluded that the effect of sample density on the electrical conductivity is mainly due to the grain boundary conductivity; and the effect of sample grain size （from 60 nm to 4 μm） on the electrical properties is not so significant.