Delafossite structure

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. 

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. 

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.

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 ... 

Figure 4.26 Illustration of the CuCr02 delafossite structure. The CrOg layers (shown as polyhedra) are linked through O-Cu-0 dumbbells...

Fig. 3 shows the XRD patterns of the CuCrOi powders synthesized using the GNP route at various GN ratios (1.2-1.7), and chemically treated with nitric acid. These XRD patterns indicated that the CuCr02 retained its delafossite structure after chemical treatment with nitric acid. 

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... 

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. 

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. 

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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