Synthesis and Characterization of Thorium-doped Nd2Zr2O7 Pyrochlore

doi:10.15541/jim20140240

Abstract

Abstract:

A₂Zr₂O₇ zirconate pyrochlores are proposed as potential host phases for the immobilization of high level nuclear waste because of their chemical and radiation stabilities. Thorium-doped pyrochlore Nd_1.8Th_0.2Zr₂O_7.1was synthesized at 1200℃ for 12 h by citrate polymer precursor method using zirconium nitrate, thorium nitrate, neodymium nitrate and citrate acid as raw materials. The phase compositions of the products were characterized by XRD, SEM, FT-IR and Raman spectrum. The results reveal that neodymium ions are substituted by thorium ions at the A position of A₂Zr₂O₇, which maintain the single pyrochlore structure. The lattice parameter decreases for Nd₂Zr₂O₇pyrochlore with the addition of 20at% Th because the effective ionic radius of Th⁴⁺ is less than that of Nd³⁺. The mean grain sizes of these samples are about 50 nm and the bulk densities are more than 95% of theoretical values. With thorium content increase, the degree of structural disorder in Nd_1.8Th_0.2Zr₂O_7.1pyrochlore increases.

Key words: zirconate pyrochlore, pyrochlore structure, Nd1.8Th0.2Zr2O7.1, structural disorder

CLC Number:

O731
TL93

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.

Figures/Tables 7

Fig. 1 XRD patterns of precursor powder and Nd1.8Th0.2Zr2O7.1 samples sintered at different conditions. Rhombns indicate the superstructure peaks

Table 1 Lattice parameters and crystallite sizes of samples prepared at different conditions

Composition	Calcination condition	Crystal size/nm	Lattice parameter/nm
Nd₂Zr₂O₇	1200℃/12 h	45.8	1.0674
Nd_1.8Th_0.2Zr₂O_7.1	Precursor	9.3	-
Nd_1.8Th_0.2Zr₂O_7.1	1000℃/6 h	9.5	-
Nd_1.8Th_0.2Zr₂O_7.1	1200℃/6 h	15.9	-
Nd_1.8Th_0.2Zr₂O_7.1	1200℃/12 h	45.4	1.0634

Fig. 2 XRD patterns of Nd1.8Th0.2Zr2O7.1 and Nd2Zr2O7 samples sintered at 1200℃ for 12 h. (Rhombns indicate superstructure peaks)

Fig. 3 Raman spectra of Nd1.8Th0.2Zr2O7.1 and Nd2Zr2O7 samples sintered at 1200℃ for 12 h

Fig. 4 FT-IR spectra of Nd1.8Th0.2Zr2O7.1 (a, b, c, d) and Nd2Zr2O7 (e) samples sintered at different conditions

Fig. 5 SEM images and EDS analyses of Nd2Zr2O7 (a) and Nd1.8Th0.2Zr2O7.1(b) samples sintered at 1200℃ for 12 h

Fig. 6 Elements distribution image (a) and backscattered electron micrograph (b) of Nd1.8Th0.2Zr2O7.1. Red is Zr; Green is Nd; Blue is Th

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Synthesis and Characterization of Thorium-doped Nd₂Zr₂O₇ Pyrochlore

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