Synthesis, Characterization, and Crystal Structure Refinement of Lanthanum and Yttrium Substituted Polycrystalline 2M Type Zirconolite Phases: Ca1-xMxZrTi2O7(M = Y, La andx= 0.2)

Crystalline ceramics are intensively investigated as effective materials in various nuclear energy applications, such as inert matrix and accident tolerant fuels and nuclear waste immobilization. This paper presents an analysis of the current status of work in this field of material sciences. We have considered inorganic materials characterized by different structures, including simple oxides with fluorite structure, complex oxides (pyrochlore, murataite, zirconolite, perovskite, hollandite, garnet, crichtonite, freudenbergite, and P-pollucite), simple silicates (zircon/thorite/coffinite, titanite (sphen), britholite), framework silicates (zeolite, pollucite, nepheline /leucite, sodalite, cancrinite, micas structures), phosphates (monazite, xenotime, apatite, kosnarite (NZP), langbeinite, thorium phosphate diphosphate, struvite, meta-ankoleite), and aluminates with a magnetoplumbite structure. These materials can contain in their composition various cations in different combinations and ratios: Li–Cs, Tl, Ag, Be–Ba, Pb, Mn, Co, Ni, Cu, Cd, B, Al, Fe, Ga, Sc, Cr, V, Sb, Nb, Ta, La, Ce, rare-earth elements (REEs), Si, Ti, Zr, Hf, Sn, Bi, Nb, Th, U, Np, Pu, Am and Cm. They can be prepared in the form of powders, including nano-powders, as well as in form of monolith (bulk) ceramics. To produce ceramics, cold pressing and sintering (frittage), hot pressing, hot isostatic pressing and spark plasma sintering (SPS) can be used. The SPS method is now considered as one of most promising in applications with actual radioactive substances, enabling a densification of up to 98–99.9% to be achieved in a few minutes. Characteristics of the structures obtained (e.g., syngony, unit cell parameters, drawings) are described based upon an analysis of 462 publications.

show abstract

“…5. Zirconolite [112,113,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150], Figure 5.…”

Section: Crystalline Ceramic Phasementioning

confidence: 99%

Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization

2019

View full text Add to dashboard Cite

show abstract

“…These studies mainly focused on the structural relationship like phase change between the zirconolite and the pyrochlore system with dopant concentration. Bohre et al [23] studied the structural behavior of zirconolite Ca 0.8 M 0.2 ZrTi 2 O 7 (where M=La, Y) with 20% substitution of Ln 3+ and Y 3+ on Ca site. However, they reported structural information without any charge balance in the structure that critically affects the single-phase behavior of zirconolite.…”

Section: Introductionmentioning

confidence: 99%

Structural and electronic behavior of yttrium doped zirconolite ceramic; a potential waste form for burning minor actinides

Kaur¹,

Gupta²,

Kulriya³

et al. 2022

Phys. Scr.

View full text Add to dashboard Cite

In the study of nuclear materials, zirconolite ceramic doped with yttrium, as a surrogate for minor actinides, is chosen to study the effects of doping on structural and electronic response which are crucial parameters in the determination of the stability and durability of materials under radiation effects. The sample Ca0.9Zr0.9Y0.2Ti2O7 have been synthesized using conventional solid-state route of two-step sintering process. X-ray diffraction and Raman spectroscopy studies are performed on samples to examine the effect of temperatures on formation of phase. The scanning electron microscopy analysis revealed formation of porous micro-structure at 1200 °C while dense-packed morphology at sintering temperature of 1300 °C. Both XRD and Raman spectroscopy on samples sintered at 1300 oC reveal almost single phase (2M zirconolite) formation with 20 % molar concentration of yttrium thus indicating high loading capacity of zirconolite. The formation of 2M-zirconolite phase is also confirmed from Rietveld refinement of the spectra. Analysis of refinement of spectra of sample sintered at 1300 °C indicates substitution of Y3+ ions against both Ca and Zr sites with similar occupancy of ~10%, while the altered chemical environment is found to affect the bond length. XPS confirms the presence of Y3+ in the structure and illustrates further that oxidation states of all the elements remain unaltered. Finally, the measurements and analysis show that zirconolite can retain its structural integrity by incorporation of 20 % molar concentration of yttrium on Ca and Zr sites and can be a promising waste form for burning the minor actinides in advance accelerators.

show abstract