Delafossite

The interest in the synthesis and properties of delafossite structured compounds that have the general formula of ABO2 have grown due to their p-type conductivity and optical transparency. The application of ultrasound for the synthesis of ternary oxide AgMC>2 (M = Fe, Ga) has been investigated by Nagarajan and Tomar [44]. Above materials were obtained in crystalline form within 40-60 min of sonication. 

Sheets, W.C., Mugnier, E., Barnabe, A., Marks, T.J. and Poeppelmeier, K.R. (2006) Hydrothermal synthesis of delafossite-type oxides. Chemistry of Materials, 18, 7-20. 

Recently, a detailed study4,5 of AB02 compounds confirms that AgFe02 has the CuFe02 (delafossite) structure. The cell dimensions, determined with a Guinier camera, are found to be a = 3.0391 2 A. and c = 18.590 2 A. Single crystals are used to measure resistivity as a function of temperature.6 Silver fer-rate(III) exhibits semiconductor behavior with an activation energy of 0.7 e.V. An unusual anisotropy in resistivity is found withp(j c) = 3 X 107 S2-cm. and P( c) = 2 X 1010 J2-cm. 

Relatively few ternary palladium oxides have been reported in the literature. Various alkali metal-palladium oxides are known (14,15,16). Intermediate compounds have been found in several Ln203-Pd0 systems with Ln = La, Nd, Sm, Eu, Gd, and Dy (3). At high pressures, pyrochlores of the type Ln2Pd207 can be prepared (19). Recently, the delafossite-like compounds PdCo02, PdCr02, and PdRhOo have been studied (18). 

In this catch-all Section, we mainly discuss the spinel structures with the generic formulas, AB2O4 and A2MO4. The unit cell of the spinel structure is a large cube, eight times (2x2x2) the size of a typical face centered cube.385 We also discuss the delafossite-type structure ABO 2 in which the A cation is in linear coordination... 

Figure 3.16. The hexagonal delafossite structure. Lightly shaded circles are oxygen atoms. The dark circles in the centers of the octahedra are the B atoms. The A atoms are the gray circles located between the slabs of edge-sharing SOg octahedra.

Cuprous ferrite, CuFe02 or Cu2O.Fe2Oa, occurs as the mineral delafossite in Arizona.3 It yields tetragonal crystals,... 

On the basis of both interatomic distances and physical properties it would seem justifiable to subdivide the compounds with structure (b) of Table 6.7 (Fig. 6.22(d)) into two classes. There are numerous oxides with this structure, sometimes called the delafossite structure after the mineral CuFe02 ... 

T24.5 Delafossite is a mineral with chemical composition CuFe02- Its structure has been described in Pabst, A. (1938) American Mineralogist, 23, 175-176, and more recently revisited (with a look at electronic properties of this material) in Marquardt, M., Ashmore, N Cann, D. (2006). Thin Solid Films, 496(1), 146-156. Connect this research with the fact that Fe 03 can also be used as a photocatalyst, as mentioned in Section 24.17 Photocaialysis. 

Tsuboi N., Takahashi Y., Kobayashi S., Shimizu H., Kato K. and Kaneko F. (2003), Delafossite CUAIO2 films prepared by reactive sputtering using Cu and A1 targets , J. Phys. Chem. Solids 64, 1671-1674. 

Lithium azide, LiN,. has the delafossite (CuFeC)2) structure (with N, replacing linear O Cu O groups) the metal atoms center octahedra [37], The... 

Azides also present interesting analogies to other compounds with linear groups, and we have pointed out the structural similarities of some azides with oxides with O-Cu-O groups (delafossites) and with linear F-H-F groups. 

The latest systems appear to work under visible light illumination without a noble metal-based H2 and/or O2 catalyst There have been reported photocatalysts such as delafossite CuFe02, without a separate H2 or O2 catalyst, or In/NiAra-oxides coated with NiO, or RUO2 for visible-light activated water-splitting processes. However, all reported water-splitting systems are controversial and require confirmation [3]. 

The T,CuFe02 rhombohedral ferrite, known as delafossite, presents an incongraent melting at 1180°C [1996Zha2, 1997Zha2]. However, it must be pointed out that its stability domain is strongly dependent... 

In their ab initio study on CUMO2 (M=A1, Ga, Y) delafossite-type oxides Buljan et a/. analysed the bonding in the Cu layers. The topological analysis revealed the existence of weak attractive d -d interactions that were suggested... 

In 2012, Burlet et al. showed that strong spectroscopic evidence proved that the mineral structure could be better described by the chemical formula HC0O2 instead of CoO.OH [5]. The mineral should be thus considered as a cobaltic acid [12] instead of a cobalt oxy-hydroxide [3]. Heterogenite was in consequence categorized as a layered oxide with a delafossite-type structure [5]. 

Burlet C., Vanbrabant, Y., Goethals, H, Heterogenite (HC0O2) delafossite crystal structure and polytypic differentiation (Spec. Acta Part. A., 2012), submitted... 

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