Interstitial oxygen conduction in lanthanum oxy-apatite electrolytes
Interstitial oxygen conduction in lanthanum oxy-apatite electrolytes
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DOI：
10.1039/b315257j
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发表时间：
2004-01-01
影响因子：
--
通讯作者：
Aranda, MAG
中科院分区：
文献类型：
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作者：
León-Reina, L;Losilla, ER;Aranda, MAG
制备了La_（10-x）（SiO_4）（6）O_（3 - 1.5）x（9.33 ≤ 10 - x ≤ 9.73）系列磷灰石，在较窄的组成范围（9.33 ≤ 10 - x ≤ 9.60）内得到六方单相。La-9.55（SiO 4）（6）O-2.32的室温晶体结构已由中子和实验室X射线粉末衍射数据的联合Rietveld精修确定：a = 9.7257（1）埃，c = 7.1864（1）埃，V = 588.68（1）埃（3），Z = 1，R-wp（N）= 3.2%，R-wp（X）= 7.7%，R-F（N）= 1.8%，R-F（X）= 1.9%。一个额外的氧间隙网站已被确定在最近预测的位置在理论研究中使用原子模拟。高温晶体结构已获得中子粉末衍射，NPD，收集在773和1173 K显示热演化的间隙网站。以前报道的La-9.60（GeO 4）（6）O-2.40的中子数据也被重新分析，建立了这个间隙位置的存在和热演化。电性能测试结果表明，样品为氧离子导体.阻抗的虚部Z”和电模量的虚部M”与log（频率）的关系图对于两条曲线都具有最大值，这两条曲线在频率上相隔20倍。体电导率已获得从拟合的复阻抗谱与适当的等效电路。体活化能已由两个Arrhenius图确定，一个表示体电导率，另一个表示模量峰最大值f（max）（M”）的频率。对两个系列La_（10-x）（TO_4）（6）O_（3 -1.5x）（T = Si，Ge）进行了比较讨论。
The La10-x(SiO4)(6)O3-1.5x (9.33 less than or equal to 10 - x less than or equal to 9.73) apatite series has been prepared and hexagonal single phases were obtained in a narrow compositional range (9.33 less than or equal to 10 - x less than or equal to 9.60). The room temperature crystal structure of La-9.55(SiO4)(6)O-2.32 has been determined from joint Rietveld refinement of neutron and laboratory X-ray powder diffraction data: a = 9.7257(1) Angstrom, c = 7.1864(1) Angstrom, V = 588.68(1) Angstrom(3), Z = 1, R-wp(N) = 3.2%, R-wp(X) = 7.7%, R-F(N) = 1.8%, R-F(X) = 1.9%. An interstitial site for the extra-oxygen has been determined in the position very recently predicted in a theoretical study using atomistic simulations. The high temperature crystal structures have been obtained from neutron powder diffraction, NPD, collected at 773 and 1173 K showing the thermal evolution of this interstitial site. Previously reported neutron data for La-9.60(GeO4)(6)O-2.40 have also been re-analysed establishing the existence, and thermal evolution, of this interstitial site. The electrical results suggest that the samples are oxide ion conductors. The plots of the imaginary parts of the impedance, Z", and the electric modulus, M", vs. log ( frequency), possess maxima for both curves separated by two decades in frequency. Bulk conductivities have been obtained from the fitting of the complex impedance spectra with the appropriate equivalent circuit. Bulk activation energies have been determined from two Arrhenius plots, one representing the bulk conductivities and the other representing the frequencies of the modulus peak maxima, f(max)(M"). A comparative discussion of the two series, La10-x(TO4)(6)O3-1.5x (T = Si, Ge), is given.