On AgRhO2, and the new quaternary delafossites AgLi1/3M2/3O2, syntheses and analyses of real structures

Two new quaternary delafossite type oxides with the general formula Ag(Li1/3M2/3)O2, M=Rh, Ir, have been synthesized, and their structures characterized. Based on X-ray and electron diffraction analyses the structural similarity with AgRhO2 delafossite, has been evidenced. The real structures of the quaternary delafossites have been revealed, which has allowed to fully explain the diffuse scattering as observed in X-ray powder diffraction. AgRhO2 is thermally stable up to 1173 K, the behavior of the two quaternary compounds AgLi1/3Rh2/3O2 and AgLi1/3Ir2/3O2 is comparable, and they decompose above 950 and 800 K, respectively. AgRhO2 shows temperature independent paramagnetism, while for the other two an effective magnetic moment of 1.77μB for Ir, and 1.70μB for Rh were determined, applying the Curie–Weiss law. All compounds are semiconducting with activation energies of 4.97 kJ mol−1 (AgLi1/3Rh2/3O2), 11.42 kJ mol−1 (AgLi1/3Ir2/3O2) and 17.58 kJ mol−1 (AgRhO2).

graphical abstractTwo new quaternary delafossite type oxides with the general formula Ag(Li1/3M2/3)O2, M=Rh, Ir, have been synthesized, and their structures characterized. The real structures of the quaternary delafossites have been revealed, which has allowed to fully explain the diffuse scattering as observed in X-ray powder diffraction.Figure optionsDownload as PowerPoint slideHighlights
► Analysis of the real structures of the Ag(Li1/3Rh2/3)O2 and Ag(Li1/3Ir2/3)O2.
► Diffuse scattering has been rationalized by severe disorder in the stacking sequences.
► The oxygen atom layer stacking sequence needs to change.