The structure and electrical properties of lithium doped pyrochlore Gd2Zr2O7

Anokhina, I. A.; Анимица, И. Е.; Воронин, В. И.; Выходец, В. Б.; Куренных, Т. Е.; Молчанова, Н. Г.; Вылков, А. И.; Dedyukhin, Alexander; Zaikov, Yu. P.

doi:10.1016/j.ceramint.2020.09.025

Cited by 25 publications

(16 citation statements)

References 62 publications

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“…As can be seen, there is a nonmonotonic dependence. The lattice parameter increases slightly for the composition x = 0.03 in comparison with undoped gadolinium zirconate [42] and then decreases monotonically. This suggests that different substitution mechanisms are realized depending on the concentration of the dopant.…”

Section: Structural Featuresmentioning

confidence: 92%

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

et al. 2022

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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.

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Section: Structural Featuresmentioning

confidence: 92%

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

et al. 2022

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“…The initial ZrO 2 powder (67 at.% oxygen) and Li 2 ZrO 3 (33.3 at.% lithium) were served as etalon samples. 29 The concentrations were calculated using tabulated data according to the stopping power of the elements.…”

Section: Methodsmentioning

confidence: 99%

Reduction of ZrO₂ during SNF Pyrochemical Reprocessing

Nikolaev

Suzdaltsev

Pavlenko

et al. 2021

J. Electrochem. Soc.

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Reduction of ZrO 2 by lithium during electrolysis of LiCl-KCl-Li 2 O melt at 650°C was studied using a set of physicochemical methods of analysis. Influence of ZrO 2 in the space near a molybdenum cathode on the kinetics of the cathode process was established. Possible variations of the electrode reaction associated with the zirconium reduction were proposed. The appearance of ZrO 2 in the cathode space resulted in consumption of reduced lithium and in increase in the potential relaxation time of the molybdenum cathode after cathode polarization. Long-term galvanic impulse electrolysis of LiCl-KCl-Li 2 O melt at 650°C was carried out using the molybdenum cathode which was immersed into the ZrO 2 powder. According to the X-ray fluorescence analysis as well as the method of nuclear reactions the reduction product was presented by the ZrO 2 , Li 2 ZrO 3 , Zr 3 O phases. Additionally, by alloying the reduction product with tin, the ZrO 2 reduction degree to metallic zirconium was estimated, which was close to zero. It was assumed that the main pathway for the appearance of the metallic zirconium in the ZrO 2 reduction product during electrolysis of the LiCl-KCl-Li 2 O melt was direct electroreduction of dissolved zirconium in the melt.

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“…Since high-temperature annealing was not performed in order to preserve the stoichiometry of solid solution with respect to lithium and the relative density was ~70%, data on the electrical conductivity of samples with the same relative density were used for a correct comparison to matrix phase Gd 2 Zr 2 O 7 . The electrical conductivities of Gd 2 Zr 2 O 7 samples with different relative densities were presented in [19].…”

Section: Electrical Measurementsmentioning

confidence: 99%

Electrical Properties of Li+-Substituted Solid Solutions Based on Gd2Zr2O7

Anokhina

Анимица

Воронин

et al. 2021

Russ. J. Phys. Chem.

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Solid solution $${\text{G}}{{{\text{d}}}_{{2 - x}}}{\text{L}}{{{\text{i}}}_{x}}{\text{Z}}{{{\text{r}}}_{2}}{{{\text{O}}}_{{7 - x}}}$$ with a pyrochlore structure is synthesized for the first time. The cationic composition is confirmed via chemical analysis and nuclear reactions. It is found that the stoichiometry with respect to lithium is retained up to 1100°C. The lattice parameter diminishes in the homogeneity range 0 ≤ x ≤ 0.30, while the free volume of migration grows. Introducing lithium into the Gd sublattice raises oxygen–ion conductivity, due to the emergence of oxygen vacancies and enhancement of their mobility. Maximum conductivity is reached for composition with х = 0.10 (~1 × 10−3 Ω−1 cm−1, 650°C). An assumption is made about the formation of associates of the type $${{\{ {\text{Li}}_{{{\text{Gd}}}}^{{''}} \cdot {\text{V}}_{{\text{o}}}^{{ \bullet \bullet }}\} }^{ \times }}$$ at high contents of the dopant (x = 0.30), accompanied by an increase in the activation energy of conductivity.

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The structure and electrical properties of lithium doped pyrochlore Gd2Zr2O7

Cited by 25 publications

References 62 publications

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

Reduction of ZrO₂ during SNF Pyrochemical Reprocessing

Electrical Properties of Li+-Substituted Solid Solutions Based on Gd2Zr2O7

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The structure and electrical properties of lithium doped pyrochlore Gd2Zr2O7

Cited by 25 publications

References 62 publications

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

Reduction of ZrO2 during SNF Pyrochemical Reprocessing

Electrical Properties of Li+-Substituted Solid Solutions Based on Gd2Zr2O7

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Reduction of ZrO₂ during SNF Pyrochemical Reprocessing