Ruthenium(V) Oxides from Low‐Temperature Hydrothermal Synthesis

Abstract

Low-temperature (200 °C) hydrothermal synthesis of the ruthenium oxides Ca1.5 Ru2 O7 , SrRu2 O6 , and Ba2 Ru3 O9 (OH) is reported. Ca1.5 Ru2 O7 is a defective pyrochlore containing Ru(V/VI) ; SrRu2 O6 is a layered Ru(V) oxide with a PbSb2 O6 structure, whilst Ba2 Ru3 O9 (OH) has a previously unreported structure type with orthorhombic symmetry solved from synchrotron X-ray and neutron powder diffraction. SrRu2 O6 exhibits unusually high-temperature magnetic order, with antiferromagnetism persisting to at least 500 K, and refinement using room temperature neutron powder diffraction data provides the magnetic structure. All three ruthenates are metastable and readily collapse to mixtures of other oxides upon heating in air at temperatures around 300-500 °C, suggesting they would be difficult, if not impossible, to isolate under conventional high-temperature solid-state synthesis conditions.

Fundamental Insights from a Single‐Crystal Sodium Iridate Battery

“…Refinement of Na‐326 was possible only by modeling it as a highly disordered phase, while Na‐113 is well‐ordered and adopts an unexpected structure, in which the honeycomb layers stack in an “eclipsed” formation with Na sitting in tunnels. This arrangement is reminiscent of structure of SrRu 2 O 6 , although the Sr sites in the honeycomb layers in this phase are vacant . TEM analysis ( Figure 2 a and Section S4, Supporting Information) further corroborates the structural assignment of this eclipsed O1 ‐type Na‐113 phase from single‐crystal XRD.…”

Antiferromagnetism atT>500Kin the layered hexagonal ruthenateSrRu2O6Hiley1, Scanlon2, Sokol3 et al. 2015Phys. Rev. B493340View full textAdd to dashboardCite

“…The interest in ruthenates is part of a wider focus on the magnetism of 4d and 5d oxides, which differ considerably from the more widely studied 3d oxides when effects such as strong spin-orbit coupling are considered [18]. Recently, some of us reported the synthesis of some new ruthenium(V) oxides using solution chemistry, among which was the hitherto unreported SrRu 2 O 6 [19]. This adopts the PbSb 2 O 6 -type structure, consisting of two oxygen layers in a hexagonal unit cell, with Ru occupying 2/3 of voids within one layer, while Sr occupies 1/3 voids in the second layer.…”

Understanding the molecular basis for the controlled design of ruthenium nanoparticles in microporous aluminophosphates

“…Further there is still no feature attributed to the Ru-Ru signal at 3.1 Å, which would appear on dehydrating RuO2.xH2O, thus confirming the difference between the RuAlPO-5-AS species and RuO2.xH2O. [35] Above 179 o C a rapid change in environment occurs ( Figure 4). A proportion of the ruthenium becomes reduced to isolated ruthenium metal (Figure 4), as shown by the appearance of a peak at 2.4 Å in Figure 2B, indicative of a metallic Ru-Ru scattering path.…”

“…[34] These observations confirm that ruthenium species in RuAlPO-5-AS primarily possess characteristics of Ru(IV)O2, with the possibility of some contribution from lower oxidation states. [35,36] This is not uncommon in AlPO chemistry, as the catalytic potential of substituted first row transition metals (Co, Mn, etc.) derives from their ability to exist in multiple oxidation states.…”