Thermodynamic investigations on the growth of CuAlO2 delafossite crystals

Wolff, Nora; Klimm, D.; Siche, D.

doi:10.1016/j.jssc.2017.11.014

Cited by 15 publications

(22 citation statements)

References 29 publications

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“…Copper can exist in the melt with oxidation states +2, +1 and 0, as shown in Fig. 6 of [22], but with recent thermodynamic data for copper oxide melts [2] one finds that, under the conditions of CuFeO 2 growth, > 90% of the copper atoms are Cu + , which is the same valency as in the solid.…”

Section: Discussionmentioning

confidence: 88%

“…Fig. 4 in our recent paper [22] shows DTA/TG heating curves for several Cu 2 O-Al 2 O 3 mixtures, and the peritectic melting of CuAlO 2 can clearly be seen as an endothermic peak near 1230 − 1250 • C for the samples with 6% and 10% Al 2 O 3 . The melting peak is always accompanied by a small mass gain.…”

Section: Discussionmentioning

confidence: 92%

“…According to the structural parameters, CuAlO 2 (R3m, a = 2.8571Å, c = 16.940Å [4]) would be the most suitable substrate material for PdCoO 2 . Unfortunately, the melt growth of bulk CuAlO 2 crystals with sufficient size is impossible, because the substance melts peritectically under the formation of solid Al 2 O 3 and the growth window (= CuAlO 2 liquidus) between the peritectic and eutectic points is too small [22,23]. The melting points of iron is the only delafossite compound, that has already be grown with reasonable quality in diameters up to 5-8 mm by the optical floating zone (OFZ) technique [25,27,28].…”

Section: Introductionmentioning

confidence: 99%

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Growth of CuFeO2 single crystals by the optical floating-zone technique

Wolff

Schwaigert

Siche

et al. 2020

Journal of Crystal Growth

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CuFeO 2 single crystals up to 50 mm in length and up to 10 mm in diameter were grown by the optical floating-zone method. Stoichiometric polycrystalline rods with a diameter of 6-12 mm were used as feed materials to produce crystals of sufficient size to be used as substrates for the growth of thin films of delafossites.For stable growth along the c-axis, low growth rates of 0.4 mm/h are necessary.Due to the incongruent melting behavior of CuFeO 2 , a stable melt zone requires adjustment of the lamp power during growth. The melting of CuFeO 2 is not simply incongruent because the thermodynamic equilibrium includes more than two solid phases and the melt; the gas phase is also involved. The crystals were characterized by X-ray diffraction and X-ray fluorescence measurements. from Catherinebourgh, Sibiria" -which instead he reported in the year 1873 to be composed from equimolar quantities of Cu + 2 O with the combination of Fe 3+ 2 O 3 , about 3.5% Al 2 O 3 [1]. This chemical composition can be written as Cu(Fe,Al)O 2 . The new mineral was given the name delafossite. In the years since Friedel's discovery a large number of other A + B 3+ O 2 compounds have become known that show basically the same structural features: BO 6 octahedra form layers that are stacked parallel to (001), and these edge-sharing octahedral sheets are connected along the [001] direction by linear O -A + -O bonds. Depending on details of the stacking sequence, the structures are usually either hexagonal or trigonal [2]. As an exception, Cu + Mn 3+ O 2 is monoclinic with space group C2/m [3]. Shannon et al. [4] revealed that not only copper and silver can acts as the A + element, but also other quite noble metals like palladium or even platinum. This is surprising because oxides of the platinum group metals are not only scarce and often unstable, but also the known platinum group binary oxides show oxidation states of 2+ or higher, e.g. PdO, PdO 2 , PtO, PtO 2 , PtO 3 , and not Pt 1+ as occours in Pt-containing delafossites.Oxide materials based on the ABO 2 delafossite structure are of particular interest due to the novel properties that accompany their cation variation at A and B sites. These properties are of interest to fundamental science [5,6,7,8,9] as well as applications [10]. Usually, the semiconductor delafossites consist of Ag or Cu at the A-site and several trivalent cations like Al, Fe or Ga at the B-site. Important among the semiconducting delafossites is CuAlO 2 with its relatively high mobility for a p-type transparent conducting oxide [11]. Pd-and Pt-based compounds (for A + ) are metallic delafossite oxides where B-site cations are transition metals like Co, Cr or Rh [4,12,13]. Among these, the growth of single crystalline PdCoO 2 has become of interest due to its ultra-high conductivity at room temperature. Recently an in-plane resistivity ρ ab = 2.6 µΩ·cm at 295 K was measured for sub-mm-sized PdCoO 2 crystals, which makes this material the most conductive oxide known, comparable to the best metallic conductors Ag, Cu, Au a...

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Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Growth of CuFeO2 single crystals by the optical floating-zone technique

Wolff

Schwaigert

Siche

et al. 2020

Journal of Crystal Growth

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“…[21][22][23][24] Figure 2 presents the results of the X-ray diffraction. The structure of the alumina range in the impregnated samples was identified, as well as slight diffraction corresponding to the copper oxide (CuO), [25][26][27][28][29][30][31] see Figure 2a. Meanwhile, the samples synthesized by sol-gel exhibited the typical diffraction of the boehmite structure, but not those of the copper oxide, instead, the formation of CuAlO 2 was favored ( Figure 2b).…”

Section: Resultsmentioning

confidence: 99%

Effect of the CuAl₂O₄and CuAlO₂Phases in Catalytic Wet Air Oxidation of ETBE and TAME using CuO/γ‐Al₂O₃catalysts

et al. 2019

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This paper studies Cu/Al 2 O 3 catalysts, synthesized in two ways: copper deposit in the synthesis of alumina (sol gel) and incipient impregnation stabilized at 400 °C. The materials were characterized by X‐ray diffraction studies, nitrogen physisorption, temperature programmed reduction of H 2 , dehydration of isopropanol, scanning electronic microscopy, transmission electronic microscopy, which were evaluated in the liquid phase oxidation reaction of ethyl tert‐butyl ether and tert‐amyl methyl ether. The formation of CuAl 2 O 4 and CuAlO 2 in the samples synthesized by sol gel, led to a modification of the texture, thus resulting in an expansion of the specific area of the materials. CuAl 2 O 4 and CuAlO 2 have been identified by DRX from a content of 10 % Copper, the first showed the highest intensity with this technique. In the same way, these species favor the presence of Lewis acid sites; this is reflected in the materials with (Di‐isopropyl Ether) DIPE of 96.7 % and 91.1 % for the samples SAlCu5 and SAlCu15 respectively. The catalytic activity of the materials prepared by sol gel is in the function of the number of surface acid sites, the smaller particle size of the Cu and the surface of the contact, in the case of the ETBE meanwhile for TAME the activity was based mainly on the strength of the present acid sites. With impregnated materials, the activity is attributed to the smaller particle size of the Cu and the greater strength of the surface acid sites in the solid. The formation of spinel species inhibits the leaching phenomenon in the reaction milieu.

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“…With the aim to crystals with sufficient size to serve as substrates we addressed the issue of crucible stability . Alumina crucibles were penetrated, and platinum proved among many other materials as the most suitable.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Investigation of Ternary Delafossite Crystals

Wolff

Klimm

Ganschow

et al. 2019

Crystal Research and Technology

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The ternary phase diagram of copper-iron-aluminium delafossite is established with FactSage calculations to improve the conditions for solution growth and the electrical conductivity of the transparent p-type semiconductor copper-aluminium delafossite by addition of iron oxide. Initial growth experiments with the optical float zone method show that the growth of single crystals with commercially relevant dimensions is not expected in the near future.

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Thermodynamic investigations on the growth of CuAlO2 delafossite crystals

Cited by 15 publications

References 29 publications

Growth of CuFeO2 single crystals by the optical floating-zone technique

Growth of CuFeO2 single crystals by the optical floating-zone technique

Effect of the CuAl₂O₄and CuAlO₂Phases in Catalytic Wet Air Oxidation of ETBE and TAME using CuO/γ‐Al₂O₃catalysts

Thermodynamic Investigation of Ternary Delafossite Crystals

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Thermodynamic investigations on the growth of CuAlO2 delafossite crystals

Cited by 15 publications

References 29 publications

Growth of CuFeO2 single crystals by the optical floating-zone technique

Growth of CuFeO2 single crystals by the optical floating-zone technique

Effect of the CuAl2O4and CuAlO2Phases in Catalytic Wet Air Oxidation of ETBE and TAME using CuO/γ‐Al2O3catalysts

Thermodynamic Investigation of Ternary Delafossite Crystals

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Effect of the CuAl₂O₄and CuAlO₂Phases in Catalytic Wet Air Oxidation of ETBE and TAME using CuO/γ‐Al₂O₃catalysts