Structural, Magnetic and Thermoelectric Properties of Delafossite-type Oxide, CuCr_1-xMg_xO₂ (0 ≤x ≤0.05)

Abstract

We report the crystal structures, magnetic susceptibilities and thermoelectric properties of a delafossite-type oxide, CuCr1-xMgxO2 (0 ≤x ≤0.05) at temperatures in the range from 4 to 1100 K. The lattice parameter, c, linearly decreases with increasing Mg concentration in the range 0 ≤x ≤0.03. This decrease is mainly caused by the shrinking of O–Cu–O dumbbells which connect the CdI2-type (Cr/Mg)O2 slabs. Magnetic susceptibility measurements indicate that Cr3+ is in the high spin state in the paramagnetic phase above 25 K. The electrical resistivity, ρ, of CuCr1-xMgxO2 exhibits semiconducting behavior (dρ/dT < 0) in the range from 350 to 1100 K, which decreases through the partial substitution of Mg2+ for Cr3+ with 0 ≤x ≤0.03. Positive and high Seebeck coefficients of CuCr1-xMgxO2 at high temperatures are consistant with the theoretical values predicted by Koshibae, who considered the spin entropy flux for the high-temperature Seebeck coefficent. From the linear S vs ln σ plot, considerable contribution from the band structure and carrier concentraton to the Seebeck coefficient is indicated. The power factor, S2σ, reaches its maximum value at around x = 0.03 in this system. The thermal conductivity, κ, for CuCr1-xMgxO2 ranges from 6 to 10 W·m-1·K-1 at 300 K, slowly decreasing with increasing temperature up to 1000 K. In the present system, the maximum dimensionless figure of merit, ZT=S2T/ρκ= 0.04, is realized for the case of x = 0.03 at 950 K.

Transparent conductive CuCrO2thin films deposited by pulsed injection metal organic chemical vapor deposition: up-scalable process technology for an improved transparency/conductivity trade-off

“…55,56 The extracted parameter a, along the (012) direction (parameter c is known thanks to the (006) direction), is 2.98 AE 0.02 Å and is in good agreement with the values reported for crystalline CuCrO 2 delafossite (2.97 Å). 23,55,56 According to the crystalline parameters a and c, our materials lattice seems to be slightly compressed along the c axis by 0.3%. A pure polycrystalline delafossite CuCrO 2 phase is grown with large process windows of precursor ratio and temperature.…”

“…Copper chromium oxides contrast with other delafossites, in terms of: (i) high density of state of 3d M cations (Cr 3+ ) near the valence band maximum, (ii) covalent mixing between chromium and oxygen ions and (iii) good dopability, [17][18][19][20][21][22] making CuCrO 2 a good p-type candidate for transparent electronic devices. Several methods were reported in the literature for the synthesis of CuCrO 2 : solid-state reaction (SS), 17,[20][21][22][23][24][25][26][27][28][29][30] sol-gel (SG), [31][32][33][34][35][36][37] pulsed laser deposition (PLD), [38][39][40][41][42] magnetron sputtering (MS) 16,[43][44][45][46] and chemical vapor deposition (CVD) including spray pyrolysis. [47][48][49][50] A summary of the electrical and optical properties versus the synthesis methods and the process temperature is given in are obtained with the films deposited by sol-gel, due to the low carrier concentration.…”

Magnetoelectric properties of multiferroic CuCrO2 studied by means of ab initio calculations and Monte Carlo simulations

“…An experimental crystal structure [37] was considered, taking into account a small in-plane lattic distortion, suggested in Ref. [29].…”

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

“…[32] In some thin-film works, Mg-substitution levels as high as 12% have been reported, clearly contradicting to the very limited substitution levels reported for bulk samples. [21,[33][34][35][36] Atomic layer deposition (ALD) is an advanced gas-phase thin-film deposition technique that affords precise film-thickness control owing to its unique deposition mechanism based on sequential and repeated exposures of precursor vapors that undergo self-limiting surface reactions. [37] Not only low deposition temperatures but also ALD offers the benefit of wafer-scale fabrication of various inorganic films, including oxides, nitrides, metals, and chalcogenides.…”