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用惰性气体蒸发和真空原位加压方法制备了两种具有清洁界面的纳米离子固体CaF_2(平均粒度为16nm)和Ca_(0.75)La_(0.25)F_(2.25)(平均粒度为11nm),在31℃至530℃详细测量了其复阻抗谱。结果表明:1)在300—530℃两种纳米离子导体都很好地遵从Arrhenius方程式;2)纳米CaF_2的离子电导率比多晶CaF_2约高1个数量级、比单晶CaF_2高2个数量级,离子导电激活能△E=1.14eV;3)纳米Ca_(0.75)La_(0.25)F_(2.25)的离子电导率比纳米CaF_2高1(300℃)至0.6(525℃)个数量级,激活能△E=1.00eV,略低于纳米CaF_2;4)从250℃升至525℃两种纳米离子导体的晶粒电阻下降约一个数量级,晶界电阻单调下降4个多数量级。表明F~-迁移在低温区(<400℃)为晶粒扩散,在高温区(>450℃)转变为晶界扩散。综上所述,将材料晶粒度减小至纳米尺度和掺杂都可明显提高离子电导率。
Two kinds of nano-ionic solid CaF_2 with a clean interface (average particle size of 16nm) and Ca_ (0.75) La_ (0.25) F_ (2.25) (average particle size of 11nm) were prepared by inert gas evaporation and vacuum in- The complex impedance spectra were measured in detail at 31 ° C to 530 ° C. The results show that: 1) Both nanocrystalline ionic conductors comply well with Arrhenius equation at 300-530 ℃; 2) The ionic conductivity of nanocrystalline CaF 2 is about one order of magnitude higher than that of polycrystalline CaF 2, which is two orders of magnitude higher than that of single crystal CaF 2, The ionic conductivity activation energy △ E = 1.14eV; 3) The ionic conductivity of nano-Ca_ (0.75) La_ (0.25) F_ (2.25) is 1 order of magnitude higher than that of nano CaF_2 to 0.6 (525 ℃) E = 1.00eV, slightly lower than that of nano-CaF_2; 4) The grain resistance of two kinds of nano-ionic conductors decreased by about one order of magnitude from 250 ℃ to 525 ℃, and the grain boundary resistance decreased monotonically by more than four orders of magnitude. It shows that the F ~ - migration is the grain diffusion in the low temperature region (<400 ℃) and the grain boundary diffusion in the high temperature region (> 450 ℃). In summary, reducing the grain size of the material to nano-scale and doping can obviously improve the ionic conductivity.