Water and hydrogen evolution properties and protonic conducting behaviors of Ca2+-doped La2Zr2O7 with a pyrochlore structure
Water and hydrogen evolution properties and protonic conducting behaviors of Ca2+-doped La2Zr2O7 with a pyrochlore structure
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DOI：
10.1016/s0167-2738(97)00433-5
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发表时间：
1997-12-01
影响因子：
3.2
通讯作者：
Otsuka-Matsuo-Yao, S
中科院分区：
文献类型：
--
作者：
Omata, T;Okuda, K;Otsuka-Matsuo-Yao, S
采用传统的陶瓷制备方法制备了具有烧绿石结构的La 2 Zr 2 O 7，即（La 2-xCax）Zr 2 O 7-δ、La-2（Zr 2-xCax）O 7-δ和（La 2-x/2Cax/2）（Zr 2-x/2Cax/2）O 7-δ。在（La 2-xCax）Zr 2 O 7-delta、La-2（Zr 2-xCax/2）O 7-delta和（La 2-x/2Cax/2）（Zr 2-x/2Cax/2）O 7-delta体系中，晶格常数随x的增加分别表现出轻微的减小、急剧的增大和轻微的增大。在这些氧化物中的质子浓度进行了评估，通过检测的放出的H2O气体，这是由热脱附，使用四极质谱仪。虽然未掺杂的La 2 Zr 2 O 7-δ没有检测到H2O、H-2或O-2气体的析出，但对于所有Ca 2+掺杂的样品观察到明显的H2O气体的析出。对于（La1.92Ca0.08）Zr 2 O 7-δ，每摩尔氧化物[H2O]中析出的H2O量为3.0 x 10（-2），对于La-2（Zr1.96Ca0.04）O 7-δ为8.4 x 10（-3），对于（La1.98Ca0.02）（Zr1.98Ca0.02）O 7-δ为8.2 x 10（-3）。此外，仅在（La1.98Ca0.02）Zr1.98O7-δ中检测到氢和氧的小但清晰的演变。结合烧绿石的结构特征，讨论了其析水量、析水起始温度和最高温度的差异。E.m.f.对具有烧结的（La1.98Ca0.02）（Zr1.98Ca0.02）O 7-δ颗粒作为固体电解质的各种气体浓差电池的测量表明，质子的平均迁移数在小于或等于873 K时为1，在1073 K时为0.82。因此，具有烧绿石结构的Ca 2+掺杂La 2 Zr 2 O 7-δ是一种很有前途的高温质子导体。
Undoped and Ca2+-doped La2Zr2O7 with a pyrochlore structure, i.e. (La2-xCax)Zr2O7-delta, La-2(Zr2-xCax)O7-delta and (La2-x/2Cax/2)(Zr2-x/2Cax/2)O7-delta, were prepared by a conventional ceramic method. Composition dependencies of a lattice parameter showed a slight decrease, a sharp increase and a slight increase with increasing x in systems of (La2-xCax)Zr2O7-delta, La-2(Zr2-xCax/2)O7-delta and (La2-x/2Cax/2)(Zr2-x/2Cax/2)O7-delta, respectively. Proton concentrations in these oxides were evaluated by detection of evolved H2O gas, which was generated by thermal desorption, using a quadrupole mass spectrometer. Although no evolutions of H2O, H-2 or O-2 gases were detected for undoped La2Zr2O7-delta, clear evolutions of H2O gas were observed for all Ca2+-doped samples. The amount of evolved H2O per mole of oxide, [H2O], was found to be 3.0 x 10(-2) for (La1.92Ca0.08)Zr2O7-delta, 8.4 x 10(-3) for La-2(Zr1.96Ca0.04)O7-delta and 8.2 x 10(-3) for (La1.98Ca0.02)(Zr1.98Ca0.02)O7-delta. Further, small but clear evolutions of both hydrogen and oxygen were detected only for (La1.98Ca0.02)Zr1.98O7-delta. Differences in the amount of evolved water, and the starting and maximum temperatures of the water evolution were discussed with reference to characteristics of the pyrochlore structure. E.m.f. measurements for various gas concentration cells with the sintered (La1.98Ca0.02)(Zr1.98Ca0.02)O7-delta pellet as a solid electrolyte showed that the mean transference number of proton was 1 at less than or equal to 873 K and 0.82 at 1073 K. Thus, Ca2+-doped La2Zr2O7-delta with a pyrochlore structure is a promising protonic conductor at high temperature.