Phase Evolution and Microstructural Studies in CaZrTi ₂ O ₇ – Nd ₂ Ti ₂ O ₇ System

Abstract

A series of compositions with general stoichiometry Ca 1− x Zr 1− x Nd 2 x Ti 2 O 7 has been prepared by high‐temperature solid‐state reaction of component oxides and characterized by powder X ‐ray diffraction and electron probe for microanalyses ( EPMA ). The phase fields in CaZrTi 2 O 7 – Nd 2 Ti 2 O 7 system and distribution of ions in different phases have been determined. Four different phase fields, namely monoclinic zirconolite, cubic perovskite, cubic pyrochlore, and monoclinic Nd 2 Ti 2 O 7 structure types are observed in this system. The 4M‐polytype of zirconolite structure is stabilized by substitution of Nd 3+ ion. The addition of Nd 3+ ions form a cubic perovskite structure‐type phase and thus observed in all the compositions with 0.05 ≤ x ≤ 0.80. Cubic pyrochlore structure‐type phase is observed as a coexisting phase in the nominal composition with 0.20 ≤ x ≤ 0.90. Only a subtle amounts of Ca 2+ and Zr 4+ are incorporated into the perovskite‐type Nd 2 Ti 2 O 7 structure. EPMA analyses on different coexisting phases revealed that the pyrochlore and perovskite phases have Nd 3+ ‐rich compositions.