Synthesis and Thermostructural Studies of a CuFe_1−xCr_xO₂ Delafossite Solid Solution with 0 ≤ x ≤ 1

Abstract

In this work, different CuFe(1-x)Cr(x)O(2) compositions with 0 <or= x <or= 1 were prepared by a standard solid-state reaction. These oxides crystallize with the delafossite structure. The phase stability and thermal behavior of the complete CuFe(1-x)Cr(x)O(2) solid solution was studied by thermogravimetric analysis and high-temperature X-ray diffraction experiments under an air atmosphere up to 1000 degrees C. For x = 0, CuFeO(2) is oxidized into the spinel (CuFe(2)O(4)) and copper monoxide (CuO) phases, whereas for x = 1, CuCrO(2) is thermally stable. For all of the intermediate compositions (0 < x < 1), complex oxidation, reduction, and phase transitions between delafossite and spinel have been observed. chromium tends to stabilize the stoichiometric delafossite phase, while iron favors the delafossite-to-spinel phase transition.

Enhanced p‐Type Transparent Semiconducting Characteristics for ALD‐Grown Mg‐Substituted CuCrO2 Thin Films

“…[34,35] As the www.advelectronicmat.de (3 of 7) 1600341 wileyonlinelibrary.com ionic radius of Mg 2+ (0.720 Å) is larger than that of Cr 3+ (0.615 Å), our observations for the continuous but not linear increases in lattice parameter c up to x ≈ 0.025 provide clear evidence for the solubility of Mg on the octahedral delafossite site in our ALD-grown Cu(Cr 1−x Mg x )O 2 thin films, but the exact extent of solubility remains somewhat ambiguous. [47] In Figure 2 we first plot the room-temperature electrical resistivity (ρ) and Seebeck coefficient (S) values as a function of x for our Cu(Cr 1−x Mg x )O 2 films (upper figure), and then show the temperature dependence of ρ and S in the lower figure for the x = 0.035 film. First, the temperature dependence of resistivity shows a purely semiconducting behavior with dρ/dT < 0, and the positive Seebeck values confirm the p-type electrical conductivity.…”

Ac conductivity and dielectric properties of CuFe1−xCrxO2 : Mg delafossite

“…where r h is the hopping distance (i.e., the Cu-Cu distance a [16]) and N c is the number density of effective charge carrier. Using (8), N c can be evaluated at room temperature and compared to the number density of Cu sites in CuFe 1-x Cr x O 2 delafossite.…”

“…CuCrO 2 delafossite is also a p-type semiconductor but with a lower intrinsic electrical conductivity (σ RT = 3.5 10 -5 S.cm -1 ) [9] due to the difficulties in intercalating oxygen into the stoichiometric delafossite structure [16]. However, the electrical conductivity can be also improved up to 220 S.cm -1 with appropriate M-site doping like in CuCr 0.95 Mg 0.05 O 2 thin film [8], by the same way than CuFeO 2 .…”

“…Previously, we studied the phase stability and thermal behaviour of the CuFe 1-x Cr x O 2 (0 x 1) solid solution by thermogravimetric analysis (TGA) and high-temperature XRD under an air atmosphere up to 1000°C in order to characterize the oxygen intercalation [16]. For 0 x < 1, two oxidations were observed.…”

Comparative study of the structural and optical properties of epitaxial CuFeO2 and CuFe1−xGaxO2 delafossite thin films grown by pulsed laser deposition methods

“…In terms of four-component delafossite compounds, there are reports which describe the growth and characterization of substitutional formations, for example CuFe 1-x Cr x O 2 [17], CuCr 1-x Ni x O 2 [18] and [19]. More specific to this work, the chemical synthesis and characterization of CuGa 1-x Fe x O 2 delafossite has been reported previously [20], where it was shown that the substitution of Ga for Fe within CuGaO 2 compounds led to a strong absorption edge measured at 1.5eV which was not observed in the host lattice material CuGaO 2 , This strong absorption was attributed to the activation of forbidden optical channels by crystal symmetry breaking within the host material rather than solely due to the hybridization of band-structures described by the empirical Vegard's law.…”