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DOE OSTI2020

Materials Data on Pr2Ir2O7 by Materials Project

Pr2Ir2O7 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Pr3+ is bonded to eight O2- atoms to form distorted PrO8 hexagonal bipyramids that share edges with six equivalent PrO8 hexagonal bipyramids and edges with six equivalent IrO6 octahedra. There are two shorter (2.28 Å) and six longer (2.57 Å) Pr–O bond lengths. Ir4+ is bonded to six equivalent O2- atoms to form IrO6 octahedra that share corners with six equivalent IrO6 octahedra and edges with six equivalent PrO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 49°. All Ir–O bond lengths are 2.04 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Pr3+ and two equivalent Ir4+ atoms to form a mixture of distorted edge and corner-sharing OPr2Ir2 tetrahedra. In the second O2- site, O2- is bonded to four equivalent Pr3+ atoms to form a mixture of edge and corner-sharing OPr4 tetrahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Searching for a route to synthesize in situ epitaxial Pr 2 Ir 2 O 7 thin films with thermodynamic methods

In situ growth of pyrochlore iridate thin films has been a long-standing challenge due to the low reactivity of Ir at low temperatures and the vaporization of volatile gas species such as IrO 3 (g) and IrO 2 (g) at high temperatures and high P O2 . To address this challenge, we combine thermodynamic analysis of the Pr-Ir-O 2 system with experimental results from the conventional physical vapor deposition (PVD) technique of co-sputtering. Our results indicate that only high growth temperatures yield films with crystallinity sufficient for utilizing and tailoring the desired topological electronic properties and the in situ synthesis of Pr 2 Ir 2 O 7 thin films is fettered by the inability to grow with P O2 on the order of 10 Torr at high temperatures, a limitation inherent to the PVD process. Thus, we suggest techniques capable of supplying high partial pressure of key species during deposition, in particular chemical vapor deposition (CVD), as a route to synthesis of Pr 2 Ir 2 O 7 .

Chemistry↗