Probing the temperature effects in the radiation stability of Nd2Zr2O7 pyrochlore under swift ion irradiation

Response of nonstoichiometric pyrochlore composition Nd1.8Zr2.2O7.1 to electronic excitations

“…On irradiation at 1 × 10 13 ions/cm 2 , both samples clearly show the irradiation-induced grain fragmentation as reported earlier. 6,23 Thus, these polycrystalline pyrochlore oxides show a unit cell contraction in response to SHI irradiation (Figure 7C). This behavior can be explained by irradiation-induced volume shrinkage at the cost of irradiation-induced nano-pores contraction or annihilation.…”

“…6 In the view of their radiation response, many pyrochlore compounds were subjected to swift heavy ions (SHIs) with a dominating electronic energy loss (S e ) comparable to high energy fission fragments. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] It has been well reported that on SHI irradiation, zirconate pyrochlores easily transformed into anion-deficient fluorite structure and exhibit more radiation tolerance over titanate pyrochlores which makes them more suitable host matrix for radionuclides. Many researchers reported the increasing radiation tolerance on increasing Zr concentration over Ti in the binary system Gd 2 Zr 2−x Ti x O 7 due to increasing probability of O-D transformation.…”

“…Therefore, our group has been studied the radiation stability of another important zirconate compound Nd 2 Zr 2 O 7 (r A /r B = 1.54) and found the irradiation-induced amorphization along with O-D transformation on subjection with 100 MeV 107 Ag 9+ ions. The rate of amorphization is found to be slow at nuclear reactor temperature ∼1000 K. 23 The amorphization process is also retarded by nano-sized structure Nd 2 Zr 2 O 7 on subjection with 100 MeV Iodine ions. 6 Recently, Anithakumari et al reported an enhancement of ionic conductivity for Nd 1.8 Zr 2.2 O 7.1 by accumulating disordering without distorting pyrochlore superstructural ordering.…”

Research of Structural, Strength and Thermal Properties of ZrO2—CeO2 Ceramics Doped with Yttrium

“…One of the areas of research in the field of searching for and studying the properties of new types of materials based on oxide matrices is the creation of composite structures having several types of phases-the so-called cermets-which have a set of properties of components used in their production as well as increased resistance to external influences [24][25][26][27][28][29][30].…”

Structural Evolution and Chemical Durability of Thorium-incorporated Nd2Zr2O7 Pyrochlore at A and B Sites

“…Key words: pyrochlore; thorium; structural evolution; chemical durability; A-site substitution; B-site substitution 高放废物(HLW)中长寿命放射性锕系核素的安 全处理处置已成为制约核工业可持续发展主要障碍 之一。 高放废物安全固化要求基材具备优异的物理、 化学、抗辐照稳定性, 其中人造岩石(Synroc)固化技 术直接将核素固化到矿相晶格位置, 是高放废物固 化处理的理想方案 [1][2][3] 。Wang 等 [4] 研究发现类萤石 结构 A 2 B 2 O 7 烧绿石陶瓷可以耐受质量分数 10%的 239 Pu 近 3000 万年辐照剂量仍能保持较好的结构稳 定性, 因此烧绿石成为锕系核素固化的潜在候选基 材 [5][6][7] 。A 2 B 2 O 7 烧绿石结构(Fd-3m)是一种缺陷的萤 石结构(AX 2 ), A、B 位为金属阳离子(过渡金属或稀 土离子), 其中 A 位占据 16c 晶格位(0, 0, 0), 与氧离 子形成八配位立方六面体结构; B 位占据 16d 晶格 位(0.5, 0.5, 0.5), 与氧离子形成六配位八面体结构。 氧离子占位为 48f(x, 0.125, 0.125)和 8a(0.125, 0.125, 0.125), 8b(0.375, 0.375, 0.375)为空位; 48f 氧离子占 位 x 具有可调性, 介于 0.3125~0.3750 之间 [8] 。 近 500 种烧绿石结构化合物被成功合成, 其中烧绿石结构 A、B 位均能实现放射性核素晶格固化, 包容+2~+5 价核素, 从而实现核素高包容量 [9] 。Belin 等 [10] 在锆 基 烧 绿 石 A 位 通 过 Am 的 晶 格 全 替 代 形 成 了 Am 2 Zr 2 O 7 固化体; Kulkarni 等 [11] 以 La 2 Zr 2 O 7 作为基 材实现了 Pu 在烧绿石 A 位晶格固化; Mandal 等 [12] 利用 Gd 2 Zr 2 O 7 作为基材实现了较小包容量 Th 在烧 绿石 A 位的替代。Kutty 等 [13] 在 Gd 2 Zr 2 O 7 的 A、B 位开展了 U 的固化研究, 烧绿石 A 位对 U 的固溶量 为 10%(原子分数); B 位固溶量较低, U 掺杂导致烧 绿石结构快速转变为萤石结构。Tang 等 [14] [17] , 能更好地包容锕系核素。锕系核 素 Th 作为重要核燃料, 随着先进重水堆(AHWR) [18] 及第四代反应堆钍基熔盐堆(TMSR) [19] [21] 。采用英国 Renishaw 公司的 [22] , 531)), 未观测到其他物相结 构衍射峰, 说明样品形成了单一烧绿石结构固化 体。烧绿石结构 A 和 B 位阳离子半径比(r A /r B )为 1.46~1.78, 超过该比例范围, 烧绿石结构会转变为 萤石结构 [9] 。烧绿石结构中八配位和六配位 Th 4+ 离 子半径分别为 0.105 和 0.094 nm, 八配位 Nd 3+ 和六 配位 Zr 4+ 离子半径分别为 0.111、0.072 nm。与 Nd 2 Zr 2 O 7 的 r A /r B 值相比(~1.54) [15] ,…”