X-ray diffraction and Raman spectroscopic investigations on CaZrTi2O7Y2Ti2O7 system: Delineation of phase fields consisting of potential ceramic host materials

• Published in: Journal of nuclear materials 2016-07, Vol.475, p.192-199
• Main Authors: Jafar, M., Achary, S.N., Salke, Niliesh P., Sahu, A.K., Rao, Rekha, Tyagi, A.K.
• Format: Article
• Language: English
• Subjects: Nuclear waste immobilization; Phase relation; Pyrochlore; SYNROC; Zirconolite
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2016.04.016

Phase evolution from CaZrTi2O7 (zirconolite) to Y2Ti2O7 (pyrochlore) have been delineated by systematic characterization of a series of sample with composition as Ca1−xZr1−xY2xTi2O7 (0.00 ≤ x ≤ 1.00) by powder XRD, Raman spectroscopy, SEM and EDS analyses. Comparative analyses of XRD and Raman spectra revealed sequential evolution of phases with increasing concentration of Y3+ in the compositions. From the XRD studies, three distinct phase fields, namely two layer (2M) and four layer (4M) zirconolite-types and cubic pyrochlore-type are observed in between zirconolite (CaZrTi2O7) and Y2Ti2O7. 4M-zirconolite phase is observed in a narrow range of composition, viz. 0.35 ≤ x ≤ 0.40 while cubic pyrochlore type phase is observed in the compositions with x ≥ 1.20. The unit cell volume of different phases shows a non-linear increasing trend with Y3+ ion concentration which has been attributed to the distribution of cations in different structure and change in their coordination number. [Display omitted] •Phase fields in between CaZrTi2O7 and Y2Ti2O7 have been delineated.•Series of Ca1−xZr1−xY2xTi2O7 compositions have been prepared and characterized in detail.•2M-zirconolite → 4M-zirconolite → Pyrochlore transformation is established.•Solubility limit of Y3+ in different structure types have been concluded.•Promising matrices for immobilization of nuclear HLW have been delineated.