Anokhina Irina, Pavlenko Olga, Proskurnina Natal'ya, Dedyukhin Alexander, Animitsa Irina
The Institute of High Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences, 620990 Yekaterinburg, Russia.
The Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences, 620108 Yekaterinburg, Russia.
Materials (Basel). 2022 Jun 8;15(12):4079. doi: 10.3390/ma15124079.
Materials with pyrochlore structure A2B2O7 have attracted considerable attention owing to their various applications as catalysts, sensors, electrolytes, electrodes, and magnets due to the unique crystal structure and thermal stability. At the same time, the possibility of using such materials for electrochemical applications in salt melts has not been studied. This paper presents the new results of obtaining high-density Mg2+-doped ceramics based on Gd2Zr2O7 with pyrochlore structure and comprehensive investigation of the electrical properties and chemical stability in a lithium chloride melt with additives of various concentrations of lithium oxide, performed for the first time. The solid solution of Gd2−xMgxZr2O7−x/2 (0 ≤ x ≤ 0.10) with the pyrochlore structure was obtained by mechanically milling stoichiometric mixtures of the corresponding oxides, followed by annealing at 1500 °C. The lattice parameter changed non-linearly as a result of different mechanisms of Mg2+ incorporation into the Gd2Zr2O7 structure. At low dopant concentrations (x ≤ 0.03) some interstitial positions can be substituted by Mg2+, with further increasing Mg2+-content, the decrease in the lattice parameter occurred due to the substitution of host-ion sites with smaller dopant-ion. High-density ceramics 99% was prepared at T = 1500 °C. According to the results of the measurements of electrical conductivity as a function of oxygen partial pressure, all investigated samples were characterized by the dominant ionic type of conductivity over a wide range of pO2 (1 × 10−18 ≤ pO2 ≤ 0.21 atm) and T < 800 °C. The sample with the composition of x = 0.03 had the highest oxygen-ion conductivity (10−3 S·cm−1 at 600 °C). The investigation of chemical stability of ceramics in the melt of LiCl with 2.5 mas.% Li2O showed that the sample did not react with the melt during the exposed time of one week at the temperature of 650 °C. This result makes it possible to use these materials as oxygen activity sensors in halide melts.
具有焦绿石结构A2B2O7的材料因其独特的晶体结构和热稳定性，作为催化剂、传感器、电解质、电极和磁体等具有多种应用，从而引起了广泛关注。与此同时，此类材料在熔盐中用于电化学应用的可能性尚未得到研究。本文首次展示了基于具有焦绿石结构的Gd2Zr2O7获得高密度Mg2+掺杂陶瓷的新成果，以及对在含有不同浓度氧化锂添加剂的氯化锂熔体中的电学性能和化学稳定性的全面研究。通过对相应氧化物的化学计量混合物进行机械研磨，然后在1500℃退火，获得了具有焦绿石结构的Gd2−xMgxZr2O7−x/2（0≤x≤0.10）固溶体。由于Mg2+掺入Gd2Zr2O7结构的机制不同，晶格参数呈非线性变化。在低掺杂浓度（x≤0.03）时，一些间隙位置可被Mg2+取代，随着Mg2+含量的进一步增加，晶格参数的减小是由于较小的掺杂离子取代了基质离子位点。在T = 1500℃制备了密度为99%的高密度陶瓷。根据电导率随氧分压变化的测量结果，所有研究样品在宽范围的pO2（1×10−18≤pO2≤0.21 atm）和T < 800℃下均以主导的离子导电类型为特征。x = 0.03组成的样品具有最高的氧离子电导率（600℃时为10−3 S·cm−1）。对陶瓷在含有2.5 mas.% Li2O的LiCl熔体中的化学稳定性研究表明，该样品在650℃温度下暴露一周的时间内未与熔体发生反应。这一结果使得这些材料有可能用作卤化物熔体中的氧活度传感器。
