Structural characterization and thermal expansion behaviour in Dy2Ti2−xZrxO7 (0 ≤ x ≤ 2) system

The superior irradiation stability of zirconates compared to titanates has led to an investigation of the Dy 2 Ti 2-x Zr x O 7 (0 ≤ x ≤ 2) series for potential use as control rod materials. The impact of Zr 4+ substitution at the Ti 4+ -site in Dy 2 Ti 2 O 7 , particularly concerning alterations in the crystalline structure and vibrational properties, has been examined using X-ray diffraction and Raman spectroscopy. Zr 4+ incorporation retains the pyrochlore-type phase up to a nominal composition of x = 1.2, beyond which a transition to a fluorite phase occurs for x ≥ 1.6. The increase in relative intensity of Raman band at approximately 600 cm −1 with increasing Zr 4+ substitutions indicates an increase in disorder within the pyrochlore-type phases. Additionally, high-temperature X-ray diffraction reveals unusual thermal expansion behaviour in Dy 2 Ti 2-x Zr x O 7 samples, with thermal expansion coefficients for intermediate compositions exceeding those anticipated by Vegard's law.