Delafossite Phase Research Articles

Synthesis and electrical properties of CuNi0.5Ti0.5O2

This paper presents structural and electrical data on the delafossite compound CuNi0.5Ti0.5O2. Ceramics of CuNi0.5Ti0.5O2 were prepared via solid state synthesis techniques in a controlled atmosphere of pO2=10−3 atm. The compound crystallized into the 3R delafossite phase with hexagonal lattice parameters of a=3.0079 (±0.0004) Å and c=17.2543 (±0.003) Å. The electrical properties of the material are characterized by a room temperature conductivity of 2×10−6 S/cm. The conductivity exhibits an Arrhenius-like temperature dependence with an activation energy of 0.48 eV.

Photovoltage characterization of CuAlO2 crystallites

The delafossite phase of CuAlO2 has been prepared by ion exchange reaction at 475°C. The samples were characterized by x-ray diffraction, transmission electron microscopy, electron diffraction, transient and spectral photovoltage (PV), and diffuse reflectance spectroscopy. The produced CuAlO2 crystallites are p-type and of high electronic quality, i.e., no electronic transitions induced by deep states in the forbidden gap have been observed by PV. The temperature dependence of the optical band gap of CuAlO2 was measured between 80 and 600K. The band gap of CuAlO2 approximated to 0K amounts to 3.61eV. The quenching of the PV signal is thermally activated with an activation energy of 1.8eV.

Phase analysis study of copper ferrite aluminates by X-ray diffraction and Mössbauer spectroscopy

Abstract CuFe 2− x Al x O 4 (where x =0.0–0.6) have been synthesized at 950°C, 1000°C, 1050°C and 1100°C using the usual ceramic method. The Mossbauer measurements show reasonable values of magnetic as well as electric hyperfine interactions. At higher sintering temperatures, the spinel ferrite phase is partially dissociated forming delafossite phase in addition to the main matrix. The delafossite phase manifested itself as paramagnetic doublet overlapping the main Mossbauer spectra measured at room temperature. Furthermore, X-ray diffraction studies confirmed the presence of the CuFeO 2 (delafossite) phase of Cu–Al ferrite.

Preparation of Copper Aluminium Oxide by Spray Pyrolysis

ABSTRACTCopper aluminium oxide(CuAlO2) particles, a promissing p-type TCO(transparent conducting oxide), were prepared by spray pyrolysis. Delafossite phase of CuAlO2 was obtained when copper nitrate, copper acetate and copper sulfate, divalent copper precursors, were used as copper precursor and aluminium nitrate as aluminium precursors. However, when copper chloride (CuCl, a monovalent copper precursor) was used, the delafossite phase was not obtained regardless of the type of aluminium precursor. The O2-doped CuAlO2 was obtained by using oxygen as carrier gas.

Bimetallic phases from reduction of delafossite-type oxides in hydrogen

Delafossite-type mixed oxides A(I)B(III)O 2 prove to be thermally stable in inert or oxidizing atmospheres, but are easily degraded under reducing conditions, i.e. in molecular hydrogen. The nature of the products as well as the reaction temperatures directly depend on the metals present in the initial materials. By thermal analysis, X-ray and electron diffraction as well as electron microscopy it is shown that from selected ternary delafossites MRhO 2 (M=Cu, Ag, Pd) monophasic microcrystalline intermetallic compounds MRh can be generated at temperatures as low as ≈450 K. Similar reduction experiments are presented using novel quaternary delafossite phases CuRh x Al 1− x O 2 resp. CuRh x Cr 1− x O 2 as parent materials. A s reduction products, Cu-Rh-alloys and alumina or chromia are formed. The stoichiometry of the intermetallic products and the reduction temperatures are a function of x, where 0< x<1. The thermal stability of the intermetallic phases is characterized in inert atmosphere (N 2). By reoxidation experiments in O 2 the reversibility of the thermal reduction is studied. In addition, the thermal reactivity of the quaternary delafossite CuNi(II) 0.5Ti(IV) 0.5O 2 is described. As reduction products, metallic phases on titania are obtained.

O 2 Electrocatalysis on Thin Film Metallic Oxide Electrodes with the Delafossite Structure

Thin film electrodes of , , , and delafossite‐type oxides are good electrocatalysts for reduction and evolution in. reduction activity correlates with the noble metal cation , while evolution activity correlates with the transition metal cation . Electrodes were prepared by rf sputtering from metal alloy targets. The as‐sputtered films are amorphous. The delafossite phase forms on annealing in air or at 700°–850°C. Thin films are metallic with .