Phase evolution and microstructural studies in CaZrTi_2O_7 (zirconolite)-Sm_2Ti_2O_7 (pyrochlore) system

摘要

From the characterization of a series compositions with general stoichiometry as Ca_(1-x)Zr_(1-x)Sm_(2x)Ti_2O_7 (0.00 ≤x≤ 1.00), the phase evolution between zirconolite (CaZrTi_2O_7) and pyrochlore type Sm_2Ti_2O_7 has been elucidated. All the compositions were prepared by high temperature solid state reaction and characterized by powder X-ray diffraction (XRD) and electron probe for microanalyses (EPMA). Three major phase fields, namely two layer (2-M) or four layer (4-M) monoclinic zirconolite and cubic pyrochlore structure types were observed in this system. In addition, a feeble amount of perovskite type phase is found to coexist with zirconolite phase. 4-M zirconolite phase is observed as single phase field at the composition with x=0.30 and 0.35, while cubic pyrochlore phase is observed as single phase at the compositions with x ≥ 0.60. Further, the composition and microstructure of coexisting phases are verified by back scattered electron image and EPMA studies.