Synthesis and Characterization of a Neodymium Zirconate Pyrochlore Doped with Ytterbium: (YbxNd1-x)2Zr2O7 (x = 0.1, 0.25 and 0.4)

Abstract

This study deals with the solid state synthesis of neodymium zirconates, doped with ytterbium, with the chemical formulas of: (Yb x Nd 1-x) 2 Zr 2 O 7 , (x = 0.1, 0.25 and 0.4). These materials are proposed as high-level radioactive waste confinement materials. Neodymium is employed as an actinide surrogate. The synthesis process consists in successive calcination steps at: 600, 1,200, 1,300 and 1,400 °C. The end-products have a sintered density of 6,368, 6,543 and 6,674 kg/m 3 , for: (Yb 0.1 Nd 0.9) 2 Zr 2 O 7 , (Yb 0.25 Nd 0.75) 2 Zr 2 O 7 and (Yb 0.4 Nd 0.6) 2 Zr 2 O 7 , respectively. The pyrochlores X-ray diffraction patterns of an fcc pyrochlore type lattice: Fd-3m, have been identified. The differential thermal analysis of these zirconates confirms there thermal stability. The materials do not show any phase transition against heating, until 1,650 °C, and under cooling. For the whole, the measured microhardnesses (< 120 HV) and fracture toughness' (< 1.57 × 10 6 N/m 2) reveal a brittle mechanical behaviour of the studied pyrochlores.

Machine learning the lattice constant of cubic pyrochlore compounds

“…Data for analysis in Table 1 (Columns 2-9) are from the literature. 17,[63][64][65][66][67][68][69][70] The dataset has a coverage of a wide range of pyrochlores, including a large variety of ternary compounds and mixed ones with substitutions on multiple sites.…”

Synthesis and Characterization of Thorium-doped Nd$lt;inf$gt;2$lt;/inf$gt;Zr$lt;inf$gt;2$lt;/inf$gt;O$lt;inf$gt;7$lt;/inf$gt; Pyrochlore

“…这与文献 [9,17] 的研究结果一致。 Nd 1.8 Th 0.2 Zr 2 O 7.1 样品未出现新的振动峰, 说明 样品的烧绿石对称结构未发生变化, 即固溶的 Th 很好地进入烧绿石结构; E g 、A 1g 振动峰出现明显的 宽化, 意味着烧绿石结构的无序化程度增加 [9,17] 。 相对于 Nd 2 Zr 2 O 7 的振动峰, 两个 F 2g 振动峰强度几 乎没有发生变化, 而 E g 、A 1g 振动峰强度明显减弱。 E g 、A 1g 主要反映样品中 BO 6 八面体键的振动情况, 峰强度的减弱也表示样品中的烧绿石结构有序化程 度减弱, 这主要可能是掺杂 Th 4+ 的离子半径小于 Nd 3+ , 导致结构无序化。同时, 观察发现 E g 、A 1g 峰 位也向高频部分发生漂移; 研究证实, 当 A 位阳离 子半径减小, 力场的增加将导致其振动峰向高频漂 移 [22] 。对于烧绿石结构, 键结构的变化主要由于内 部结构和化学环境变化, 掺杂的 Th 引起烧绿石结 构发生重排, B-O 键长缩短, 结合力增加, 力场增加,…”