蓝宝石衬底上Gd_2O_3掺杂CeO_2氧离子导体电解质薄膜的生长及电学性能

Growth and electrical conductivity of Gd_2O_3 doped CeO_2 ion conductor electrolyte film on sapphire substrate

采用反应磁控溅射方法,在(0001)蓝宝石单晶衬底上,制备了纳米多晶Gd2O3掺杂CeO2(GDC)氧离子导体电解质薄膜,采用X射线衍射仪(XRD)、原子力显微镜(AFM)对薄膜物相、结构、粗糙度、表面形貌等生长特性进行了表征,利用交流阻抗谱仪测试了GDC薄膜不同温度下的电学性能;实验结果表明,GDC薄膜为面心立方结构,在所研究的衬底温度范围内,均呈强(111)织构生长;薄膜表面形貌随衬底温度发生阶段性变化:衬底温度由室温升高到300℃时,对应球形生长岛到棱形生长岛的转变,当完全为棱形岛生长时(300℃),生长岛尺寸显著增大;从400℃开始,则发生棱形生长岛到密集球形生长岛的转变,球形生长岛尺寸明显减小.生长形貌的转变反映着薄膜生长初期不同的成核机理,很可能与蓝宝石(0001)面的表面结构随温度变化有关;GDC多晶电解质薄膜的复平面交流阻抗谱主要源于晶界的贡献,根据Arrhenius图求得电导活化能Ea在1.2—1.5eV范围内,接近于晶界电导的活化能值,并且随衬底温度升高Ea减小(Ea300>Ea400>Ea600);电导活化能以及晶粒尺寸不同,导致GDC薄膜电导率随测试温度的变化规律不同.

Nanocrystalline Gd2O3 doped CeO2 （abbreviated as GDC ） ion conductor electrolyte thin films synthesized by reactive magnetron sputtering on （0001） sapphire substrates have been characterized by X-ray diffraction （XRD）, atomic force microscopy （AFM） and AC impedance analysis. The results show that, the f. c. c structured GDC films have strong （111 ） textures at all the substrate temperatures of our investigation while the surface morphology varied with the temperature. Small, round growth islands transform to large prismatic islands at temperatures from room temperature to 300℃, and the reverse process occurr at temperatures from 400℃ to 700℃ . This morphology change characterizing different nucleation mechanisms at the beginning of film growth is probably due to transformation of the surface structure of the （0001） sapphire at different temperatures. The AC impedance complex plane plot of the GDC film is mainly determined by grain boundary resistances. The conductivity activation energy （1.2-1.5 eV） calculated by the Arrhenius plot is close to the reported value for the grain boundary conductivity and decreases with rising substrate temperature （ Ea300 〉 Ea400 〉 Ea600 ）. Difference in activation energy and grain size for GDC films causes unequal increasing rates of electrical conductivity at higher temperatures.