High temperature structural and thermal expansion behavior of pyrochlore-type praseodymium zirconate

• Published in: International journal of hydrogen energy Vol. 40; no. 45; pp. 15672 - 15678
• Main Authors: Shukla, R., Vasundhara, K., Krishna, P.S.R., Shinde, A.B., Sali, S.K., Kulkarni, N.K., Achary, S.N., Tyagi, A.K.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 07-12-2015
• Subjects: Crystal structure; Neutron diffraction; Pyrochlore; Thermal expansion; X-ray diffraction; Pyrochlore; X-ray diffraction; Thermal expansion; Neutron diffraction; Crystal structure
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2015.09.059

In this communication we report the high temperature structural details of pyrochlore-type Pr2Zr2O7, a potential mixed electronic and ionic conducting material, as observed from the in situ variable temperature powder neutron diffraction in vacuum. The evolution of structural parameters with temperature revealed a smooth expansion of the lattice while a feeble decreasing trend in the oxygen parameters of pyrochlore structure. The analyses of the structural parameters further indicate a larger expansion of the Pr–O bonds (α = 11.32 × 10−6 K−1) compared to that of Zr–O bonds (α = 8.83 × 10−6 K−1). The temperature dependent unit cell parameters measured under vacuum deviates from those measured in air and the coefficient of axial thermal expansion (αa) of Pr2Zr2O7 lattice is 10.18 × 10−6 K−1 (in vacuum). The analyses of structural parameters indicated a larger distortion in PrO8 polyhedra compared to ZrO6 octahedra of the Pr2Zr2O7. The differences in high temperature behaviour in air and vacuum have been explained by the contributions of oxidation of Pr3+ to Pr4+.
[Display omitted]
•High temperature crystal structure of Pr2Zr2O7 has been investigated by powder neutron diffraction study.•Axial thermal expansion coefficient of Pr2Zr2O7 is 10.18 × 10−6 K−1.•Pr2Zr2O7 show lower thermal expansion coefficients in air compared to that in vacuum.•Pr–O bonds show larger expansion compared Zr–O bonds.