Synthesis and Characterization of Nonsubstituted and Substituted Proton-Conducting La6-xWO12-y
Synthesis and Characterization of Nonsubstituted and Substituted Proton-Conducting La6-xWO12-y
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DOI：
10.1021/ic401104m
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发表时间：
2013-09-16
影响因子：
4.6
通讯作者：
Serra, Jose M.
中科院分区：
文献类型：
--
作者：
Seeger, Janka;Ivanova, Mariya E.;Serra, Jose M.
混合质子-电子导体（MPEC）可用作气体分离膜以从例如发电厂中的气流中提取氢气。从不同的MPEC来看，钨酸镧陶瓷材料呈现出重要的质子-电子混合导电性。在La/W比为4.8 ~ 6.0的条件下制备了La_（6-x）WO_（12-y）（y = 1.5x + δ，x = 0.5-0.8）化合物，并在1300 ~ 1500 ℃烧结，研究了La/W比和温度对单相形成区域的影响。此外，制备了在La或W位置上取代的化合物。Ce、Nd、Tb和Y用于La位点的部分取代，而Ir、Re和Mo用于W取代。所有取代基以不同浓度施加。未取代的La 6-xWO 12-y和所有取代的La 6-xWO 12-y化合物的电导率在400-900 ℃的温度范围内在湿（2.5%H2O）和4%H-2在Ar中的干混合物中测量。在电特性的最大改善的情况下，发现在20摩尔%的替代与Re和Mo。在800 ℃下在100%H-2中处理后，化合物保持不变，如XRD、拉曼和SEM所证实。
Mixed proton-electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic-electronic conductivity. Lanthanum tungstate La6-xWO12-y (with y = 1.5x + delta and x = 0.5-0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 degrees C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La6-xWO12-y and for all substituted La6-xWO12-y compounds was measured in the temperature range of 400-900 degrees C in wet (2.5% H2O) and dry mixtures of 4% H-2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H-2 at 800 degrees C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM.