Synthesis of La2Ti2O7 Nanoscale Powder and Ceramics Based on It by Sol–Gel Synthesis and Spark Plasma Sintering

IF 1.8 3区化学 Q3 CHEMISTRY, INORGANIC & NUCLEAR Russian Journal of Inorganic Chemistry Pub Date : 2024-07-31 DOI:10.1134/s0036023624600424

O. O. Shichalin, E. K. Papynov, A. A. Belov, K. A. Pervakov, S. S. Gribanova, S. M. Pisarev, A. N. Fedorets, A. V. Pogodaev, A. O. Lembikov, Ya. G. Zernov, P. A. Marmaza, O. V. Kapustina, E. A. Gridasova, I. Yu. Buravlev

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Abstract

The use of ceramics as matrices for immobilization of radionuclides for the purpose of their safe long-term disposal or useful application is studied with an emphasis placed on phase stability, structural integrity, hydrolytic stability, etc. This work implements a combined approach based on the sol–gel citrate synthesis of nanosized La₂Ti₂O₇ powder and its subsequent spark plasma sintering to produce dense ceramics. The phase composition and structure of the nanosized La₂Ti₂O₇ powder and the ceramic samples obtained in the temperature range of 900–1300°C were studied by powder X-ray diffraction and SEM. It was shown that the conditions of synthesis of the powder ensure the formation of nanosized crystalline La₂Ti₂O₇ grains, consolidation of which under spark plasma heating is accompanied by a change in the phase composition of La₂Ti₂O₇ from a single-phase monoclinic structure to orthorhombic structure with a LaTiO₃ impurity at temperatures above 1200°C. It was found that a change in the ceramic structure is accompanied by the formation of non-porous and defect-free monolithic samples. This type of change was shown to lead to an increase in the relative density (81.3–95.7%) and compressive strength (78–566 MPa) of the ceramics. However, the hydrolytic stability decreases, as indicated by increasing La³⁺ leaching rate from 10^–7 to 10^–5 g/(cm² day). The obtained results are useful for the systematic study of materials suitable for immobilization of radioactive waste in ceramics.

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通过溶胶-凝胶合成和火花等离子烧结法合成 La2Ti2O7 纳米粉末及其陶瓷材料

摘要研究了利用陶瓷作为固定放射性核素的基质，以实现长期安全处置或有用应用的目的，重点是相稳定性、结构完整性、水解稳定性等。这项工作采用了一种基于柠檬酸溶胶-凝胶法合成纳米级 La2Ti2O7 粉末的组合方法，并随后采用火花等离子烧结法生产致密陶瓷。通过粉末 X 射线衍射和扫描电镜研究了纳米 La2Ti2O7 粉末和在 900-1300°C 温度范围内获得的陶瓷样品的相组成和结构。结果表明，粉末的合成条件确保了纳米级结晶 La2Ti2O7 晶粒的形成，在火花等离子体加热条件下，这些晶粒固结的同时，La2Ti2O7 的相组成也发生了变化，从单相单斜结构变为温度高于 1200°C 时带有 LaTiO3 杂质的正方体结构。研究发现，陶瓷结构的变化伴随着无孔和无缺陷整体样品的形成。这种变化导致陶瓷的相对密度（81.3%-95.7%）和抗压强度（78-566 兆帕）增加。然而，正如 La3+ 浸出率从 10-7 g/（cm2 天）增加到 10-5 g/（cm2 天）所表明的那样，水解稳定性降低了。所获得的结果有助于系统研究适合在陶瓷中固定放射性废物的材料。

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来源期刊

Russian Journal of Inorganic Chemistry 化学-无机化学与核化学

CiteScore

3.10

自引率

38.10%

发文量

237

审稿时长

3 months

期刊介绍： Russian Journal of Inorganic Chemistry is a monthly periodical that covers the following topics of research: the synthesis and properties of inorganic compounds, coordination compounds, physicochemical analysis of inorganic systems, theoretical inorganic chemistry, physical methods of investigation, chemistry of solutions, inorganic materials, and nanomaterials.