Phase Transition of Ln3IrO7 (Ln=Pr, Nd, Sm, Eu) and its Low-Temperature Structure

Abstract

Ternary lanthanide iridium oxides Ln 3 IrO 7 Ln Pr, Nd, Sm, and Eu were prepared and their structures were determined by X-ray diffraction measurements. At room temperature, Pr 3 IrO 7 crystallizes in an orthorhombic superstructure of cubic fluorite with the space group Cmcm. The results of the differential thermal analysis DTA and specific heat measurements show the existence of a phase transition for Ln 3 IrO 7 Ln Pr, Nd, Sm, and Eu at 262, 342, 420, and 485 K, respectively. At low temperatures, Ln 3 IrO 7 crystallizes in a monoclinic structure with the space group P2 1 n.

Praseodymium iridium oxide as a competitive electrocatalyst for oxygen evolution reaction in acid media

“…1a, all the X-ray diffraction (XRD) peaks of pre-catalyst match well with orthorhombic Pr 3 IrO 7 with unit cell parameters of a = 10.9782 Å, b = 7.4389 Å, c = 7.5361 Å (PDF No. 97-009-9670), which is one superstructure of typical cubic fluorite-type iridates Ln 3 IrO 7 (Ln = Pr, Nd, Sm, Eu) with the space group Cmcm [20]. The corresponding crystal structure is shown in Fig.…”

Complex ceramic structures. I. Weberites

“…11). Due to the fact that this type of structure does not maintain the three-dimensional BO 6 octahedral network, it is considered a weberite-type structure rather than the weberite structure, or sometimes it is reported as a La 3 NbO 7 -type structure (Rossell, 1979;Allpress & Rossell, 1979;Rooksby & White, 1964;Abe et al, 2004Abe et al, , 2006Wakeshima et al, 2004;Groen et al, 1987;Wakeshima & Hinatsu, 2006;Nishimine et al, 2007;Gemmill et al, 2007;Khalifah et al, 1999Khalifah et al, , 2000Wiss et al, 2000;Bontchev et al, 2000;Harada & Hinatsu, 2001;Harada et al, 2001;Nishimine et al, 2005;Gemmill et al, 2004Gemmill et al, , 2005Vanberkel & Ijdo, 1986;Kahnharari et al, 1995;Wltschek et al, 1996;Greedan et al, 1997;Lam et al, 2002;Plaisier et al, 2002;Lam et al, 2003;Barrier & Gougeon, 2003;Hinatsu et al, 2004;Vente & Ijdo, 1991). Table 7 lists examples of Ln 3 BO 7 and their properties that have been investigated.…”

Phase Transition in Weberite‐Type Gd3NbO7

“…It is important to note that phase transitions are commonly observed in the Ln 3 MO 7 family and there have been numerous studies especially focusing on the crystallographic aspects of Ln 3 IrO 7 , 21 Ln 3 MoO 7 , 2,3,9,32 and Ln 3 RuO 7 12,17 . In this study, high‐resolution X‐ray diffraction (XRD) was performed on Gd 3 NbO 7 powder before and after the reported phase transition to solve the space group issue, and for the first time, determine an unequivocal space group and crystal structure that is consistent with all the experimental data available (dielectric property, heat capacity, SHG, XRD, etc.).…”

“…T he Gd 3 NbO 7 belongs to a weberite‐type Ln 3 MO 7 family (where Ln is a rare‐earth element, and M is Os 5+ , Re 5+ , Ru 5+ , Re 5+ , Mo 5+ , Ir 5+ , Sb 5+ , Nb 5+ , or Ta 5+ ) 1–28 . The characteristic of this family is that MO 6 are corner linked to each other and form chains of MO 6 octahedra with parallel chains of LnO 8 distorted cubes.…”