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

doi:10.15541/jim20220077

Abstract

Abstract:

A₂B₂O₇ pyrochlore is considered as a candidate host matrix for high-level radioactive wastes due to its incorporation and physicochemical stability. Nd_1.8Th_0.2Zr₂O₇ and Nd₂Zr_1.8Th_0.2O₇ pyrochlore samples doped with 20% thorium (in molar) were successfully prepared by using spray-pyrolysis and high temperature sintering method. The structures of the synthesized immobilization were characterized, and the chemical durability tests were investigated by the MCC-1 method. Structural analyses show that samples Nd_1.8Th_0.2Zr₂O₇and Nd₂Zr_1.8Th_0.2O₇exhibit pure single pyrochlore structure. Rietveld refinement analyses show that the value of 48f oxygen site parameter of 20% thorium-doped Nd₂Zr₂O₇pyrochlore increases, which suggests that the structure is transforming from ordered pyrochlore to disordered structure, as compared with Nd₂Zr₂O₇. The Nd_1.8Th_0.2Zr₂O₇ pyrochlore structure evolution results from the distortion of the AO₈hexahedral structure, while the B-site substitution leads to partial deformation of the BO₆octahedron. The leaching experiment results show that the normalized leaching rate of thorium is as low as 10^-5g·m^-2·d^-1 after 42 d. Thorium can be well incorporated at the A and B cation sites of the Nd₂Zr₂O₇ pyrochlore structure of which the immobilization exhibits the excellent physical and chemical properties.

Key words: pyrochlore, thorium, structural evolution, chemical durability, A-site substitution, B-site substitution

CLC Number:

TQ174

WANG Lielin, XIE Hua, XIE Yuqi, HU Pingtao, YIN Wen, REN Xinyue, DING Yun. Structural Evolution and Chemical Durability of Thorium-incorporated Nd₂Zr₂O₇ Pyrochlore at A and B Sites[J]. Journal of Inorganic Materials, 2022, 37(10): 1073-1078.

Figures/Tables 8

Fig. 1 XRD patterns of samples Nd1.8Th0.2 Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

Fig. 2 SEM images and EDS elements mappings of samples Nd1.8Th0.2 Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

Fig. 3 Rietveld refinement patterns of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

Table 1 Rietveld refinement parameters of samples Nd1.8Th0.2 Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

	Nd_1.8Th_0.2Zr₂O₇	Nd₂Zr₂O₇	Nd₂Zr_1.8Th_0.2O₇
Lattice parameter/nm	1.06370(2)	1.06744(5)	1.06781(4)
Unit cell volume/nm³	1.203	1.216	1.217
x-parameter of 48f oxygen	0.3322(6)	0.3287(6)	0.3365(5)
A-O_48f bond distance	2.5932(5)	2.6285(4)	2.5713(4)
B-O_48f bond distance	2.0737(3)	2.0660(2)	2.1017(2)
A-B bond distance	3.7607(4)	3.7739(1)	3.7753(2)
A-8a bond distance	2.3029(2)	2.3110(1)	2.3118(3)
R_p	4.66%	5.17%	4.43%
R_wp	6.04%	6.79%	5.94%
χ²	2.614	1.932	2.237

Fig. 4 Structural evolution of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

Fig. 5 Raman spectra of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

Fig. 6 Raman peak intensity variation of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7 The peak intensity is normalized to the intensity of 299 cm-1

Fig. 7 Normalized release rates of Th in samples Nd1.8Th0.2Zr2O7 and Nd2Zr1.8Th0.2O7

References 31

[1]	RINGWOOD A E, KESSON S E, WARE N G, et al. Immobilization of high level nuclear reactor wastes in SYNROC. Nature, 1979, 278: 219-223. DOI URL
[2]	ORLOVA A I, OJOVAN M I. Ceramic mineral waste-forms for nuclear waste immobilization. Materials, 2019, 12(16): 2638. DOI URL
[3]	CLARK B M, TUMURUGOTI P, SUNDARAM S K, et al. Preparation and characterization of multiphase ceramic designer waste forms. Scientific Reports, 2021, 11: 4512. DOI PMID
[4]	WANG S X, BEGG B D, WANG L M, et al. Radiation stability of gadolinium zirconate: a waste form for plutonium disposition. Journal of Materials Research, 1999, 14(12): 4470-4473. DOI URL
[5]	YANG K, KEITH B, ZHU W, et al. Multicomponent pyrochlore solid solutions with uranium incorporation-a new perspective of materials design for nuclear applications. Journal of the European Ceramic Society, 2021, 41(4): 2870-2882. DOI URL
[6]	LIAN J, WANG L M, HAIRE R G, et al. Ion beam irradiation in La₂Zr₂O₇-Ce₂Zr₂O₇pyrochlore. Nuclear Instruments and Methods in Physics Research Section B, 2004, 218: 236-243.
[7]	SHARMA S K, GROVER V, TYAGI A K, et al. Probing the temperature effects in the radiation stability of Nd₂Zr₂O₇ pyrochlore under swift ion irradiation. Materialia, 2019, 6: 2589-1529.
[8]	CHAKOUMAKOS B C. Systematics of the pyrochlore structure type, ideal A₂B₂X₆Y. Journal of Solid State Chemistry, 1984, 53(1): 120-129 DOI URL
[9]	SUN J, ZHOU J, HU Z, et al. Controllable sites and high-capacity immobilization of uranium in Nd₂Zr₂O₇ pyrochlore. Journal of Synchrotron Radiation, 2022, 29: 37-44
[10]	BELIN R C, VALENZA P J, RAISON P E, TILLARD M. Synthesis and Rietveld structure refinement of americium pyrochlore Am₂Zr₂O₇. Journal of Alloys and Compounds, 2008, 448(1/2): 321-324. DOI URL
[11]	KULKARNI N K, SAMPATH S, VENUGOPAL V. Preparation and characterisation of Pu-pyrochlore: [La_1-_xPu_x]₂Zr₂O₇ (x=0-1). Journal of Nuclear Materials, 2000, 281(2/3): 248-250. DOI URL
[12]	MANDAL B P, GARG N, SHARMA S M, et al. Solubility of ThO₂ in Gd₂Zr₂O₇ pyrochlore: XRD, SEM and Raman spectroscopic studies. Journal of Nuclear Materials, 2009, 392(1): 95-99. DOI URL
[13]	KUTTY K V G, ASUVATHRAMAN R, MADHAVAN R R, et al. Actinide immobilization in crystalline matrix: a study of uranium incorporation in gadolinium zirconate. Journal of Physics and Chemistry of Solids, 2005, 66(2/3/4): 596-601. DOI URL
[14]	TANG Z, HUANG Z Y, HAN W, et al. Uranium-incorporated pyrochlore La₂(U_xMg_xZr_1-2_x)₂O₇ nuclear waste form: structure and phase stability. Inorganic Chemistry, 2020, 59(14): 9919-9926. DOI URL
[15]	LIAN J, CHEN J, WANG L M, et al. Radiation-induced amorphization of rare-earth titanate pyrochlores. Physical Review B, 2003, 68(1): 134107. DOI URL
[16]	WANG S X, LUMPKIN G R, WANG L M, et al. Ion irradiation- induced amorphization of six zirconolite compositions. Nuclear Instruments and Methods in Physics Research Section B, 2000, 166-167(2): 293-298.
[17]	NÄSTREN C, JARDIN R, SOMERS J, et al. Actinide incorporation in a zirconia based pyrochlore (Nd_1.8An_0.2)Zr₂O₇₊_x (An=Th, U, Np, Pu, Am). Journal of Solid State Chemistry, 2009, 182(1): 1-7. DOI URL
[18]	THAKUR A, SINGH B, KRISHNANI P D. In-core fuel management for AHWR. Annals of Nuclear Energy, 2013, 57: 47-58. DOI URL
[19]	DAI Z M. Thorium molten salt reactor nuclear energy system (TMSR). Molten Salt Reactors and Thorium Energy, 2017, 17: 531-540.
[20]	WANG L L, LI J B, XIE H, et al. Solubility, structure transition and chemical durability of Th-doped Nd₂Zr₂O₇ pyrochlore. Progress in Nuclear Energy, 2021, 137: 103774. DOI URL
[21]	TOBY B H, EXPGUI. A graphical user interface for GSAS. Journal of Applied Crystallography, 2001, 34: 210-213. DOI URL
[22]	ASTM. Standard test method for static leaching of monolithic waste forms for disposal of radioactive waste. Annual Book of ASTM Standards. C1220-92. 1992, 12(1): 681-695.
[23]	STRACHAN D M. Results from long-term use of the MCC-1 static leach test method. Nuclear and Chemical Waste Management, 1983, 4(2): 177-188. DOI URL
[24]	MANDAL B P, KRISHNA P S R, TYAGI A K. Order-disorder transition in the Nd_2-_yY_yZr₂O₇ system: Probed by X-ray diffraction and Raman spectroscopy. Journal of Solid State Chemistry, 2010, 183(1): 41-45. DOI URL
[25]	QU Z, WAN C, PAN W. Thermal expansion and defect chemistry of MgO-doped Sm₂Zr₂O₇. Chemistry of Materials, 2007, 19(20): 4913. DOI URL
[26]	VANDENBORRE M T, HUSSON E, CHATRY J P, et al. Rare- earth titanates and stannates of pyrochlore structure; vibrational spectra and force fields. Journal of Raman Spectroscopy, 1983, 14: 63-71. DOI URL
[27]	NANDI C, PHATAK R, KESARI S, et al. Phase evolution in [Nd_1-_xU_x]₂Zr₂O_7+δ system in oxidizing and reducing conditions: a nuclear waste form. Journal of Nuclear Materials, 2021, 556(1): 153208. DOI URL
[28]	HAYAKAWA I, KAMIZONO H. Durability of an La₂Zr₂O₇ waste form in water. Journal of Nuclear Materials, 1993, 28: 513-517.
[29]	WEBER W J, NAVROTSKY A, STEFANOVSKY S, et al. Materials science of high-level nuclear waste immobilization. MRS Bulletin, 2009, 34: 46-53. DOI URL
[30]	GONG B W, YANG K, LIAN J A, et al. Machine learning- enabled prediction of chemical durability of A₂B₂O₇ pyrochlore and fluorite. Computational Materials Science, 2021, 200: 110820. DOI URL
[31]	FENG Z Q, XIE H, WANG L L, et al. Glass-ceramics with internally crystallized pyrochlore for the immobilization of uranium wastes. Ceramics International, 2019, 45(14): 16999-17005. DOI URL

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

RichHTML

PDF (PC)

Knowledge

Abstract

Cite this article

share this article

Figures/Tables 8

References 31

Related Articles 12

Recommended Articles

Metrics

Comments

[1]	ZENG Jianjun, ZHANG Kuibao, CHEN Daimeng, GUO Haiyan, DENG Ting, LIU Kui. Preparation of (La_0.2Nd_0.2Sm_0.2Gd_0.2Er_0.2)₂Zr₂O₇ High-entropy Transparent Ceramics by Vacuum Sintering [J]. Journal of Inorganic Materials, 2021, 36(4): 418-424.
[2]	Ya-Ping SUN, Hong-Long WANG, Jian CHU, Xu WANG, She-Qi PAN, Ming ZHANG. Leaching Behavior and Mechanism of Ceramic Waste Forms [J]. Journal of Inorganic Materials, 2019, 34(5): 461-468.
[3]	WANG Lie-Lin, XIE Hua, CHEN Qing-Yun, WANG Qian, LONG Yong, DENG Chao, ZHANG Ke-Xin. Synthesis and Characterization of Thorium-doped Nd₂Zr₂O₇ Pyrochlore [J]. Journal of Inorganic Materials, 2015, 30(1): 81-86.
[4]	JIANG Jin-Long, WANG Qiong, HUANG Hao, ZHANG Xia, WANG Yu-Bao, GENG Qing-Fen. Microstructure Evolution Induced by Ultraviolet Light Irradiation in Ti-Si Codoped Diamond-like Carbon films [J]. Journal of Inorganic Materials, 2014, 29(9): 941-946.
[5]	DING Juan, LIU Rui-Heng, GU Hui, CHEN Li-Dong. Study on the High Temperature Stability of Yb_yCo₄Sb₁₂/Yb₂O₃ Composite Thermoelctric Material [J]. Journal of Inorganic Materials, 2014, 29(2): 209-214.
[6]	CHEN Pei-Rong, JI You-Zhang, YANG Qing. Preparation of Composite Additives Powder by Coprecipitation Method and Investgation of ZnO Varistor Ceramics [J]. Journal of Inorganic Materials, 2012, 27(12): 1277-1282.
[7]	HE Ming,GU Xiao-Li,LUO Zhen-Yang,LU Xiao-Hua,FENG Xin. Hydrothermal Synthesis of Polymorphic Titania and their Structural Evolution from Potassium Titanate Whisker [J]. Journal of Inorganic Materials, 2008, 23(4): 662-668.
[8]	WANG Xiu-Quan,CHEN Qi,SONG Li,LI Hui-Ping,LU Jian-Ying. WANG Xiu-Quan, CHEN Qi, SONG Li, LI Hui-Ping, LU Jian-Ying [J]. Journal of Inorganic Materials, 2006, 21(1): 181-186.
[9]	HUANG Wen-Hai,ZHOU Nai,DAY Delbcrt E,RAY Chandra S. Effect of Cr₂O₃ on the HLW Iron Phosphate Glass Wasteforms [J]. Journal of Inorganic Materials, 2005, 20(4): 842-850.
[10]	HU Ming-Zhe,ZHOU Dong-Xiang,JIANG Sheng-Lin,CAI Xue-Qing,HUANG Jing. Dielectric Properties of [(PbCa)Nd](FeNb)O₃ Microwave Ceramics [J]. Journal of Inorganic Materials, 2005, 20(1): 126-132.
[11]	YANG Qiu-Hong,KIM Eung-Soo,XU Jun. Effect of A-site Substitution by Nd~³⁺ on the Microwave Dielectric Properties of (Pb_0.5Ca_0.5)(Fe_0.5Nb_0.5)O₃ Ceramics [J]. Journal of Inorganic Materials, 2003, 18(5): 1051-1056.
[12]	WEI Jian-Zhong,CHEN Ren-Chang,ZHANG Liang-Ying,YAO Xi. Effects of Ag-Dopant on Dielectric Properties and Melting Behaviors of Bi₂O₃-ZnO-Nb₂O₅ (BZN)-Based Ceramics [J]. Journal of Inorganic Materials, 2001, 16(2): 319-323.