High-pressure electrical conductivity measurements in the copper oxides

Bourne, L. C.; Yu, Peter Y.; Zettl, A.; Cohen, Marvin L.

doi:10.1103/physrevb.40.10973

Cited by 49 publications

(31 citation statements)

References 14 publications

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“…The cell volume obtained from the refinement is found to decrease with pressure ( Figure 8) and no abrupt change is Advances in Materials Science and Engineering 7 observed indicating absence of structural transition. Literature reports indicate absence of structural transition from high-pressure electrical resistivity measurements in monoclinic CuO up to 100 GPa [36,40]. Upon increasing the pressure, at 3.98 GPa, a peak clearly separates out from the (200) plane.…”

Section: High-pressure X-ray Diffraction Using Synchrotron Radiationmentioning

confidence: 89%

“…Each pattern was fitted and refined to monoclinic structure of CuO with space group C2 1 /c using the software GSAS [34] with EXPGUI [35]. Though no structural transitions had been reported up to 100 GPa in monoclinic CuO [36][37][38][39][40], the study helps in identifying the hidden phases based on the variation in compressibility.…”

Section: High-pressure X-ray Diffraction Using Synchrotron Radiationmentioning

confidence: 99%

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Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Joseph

Venkateswaran

Vennila

2010

Advances in Materials Science and Engineering

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Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic methods. Structural and compositional analyses were performed using X-ray diffraction, SEM, and EDAX. Traces of secondary phases such as CuFe2O4, Fe3O4, andα-Fe2O3having peaks very close to that of the host CuO were identified from the Rietveld profile analysis and the SAED pattern of bulk and nanocrystalline Cu0.98Fe0.02O samples. Vibrating Sample Magnetometer (VSM) measurements show hysteresis at 300 K for all the samples. The ferrimagnetic Neel transition temperature () was found to be around 465°C irrespective of the content of “Fe”, which is close to the value of cubic CuFe2O4. High-pressure X-Ray diffraction studies were performed on 2% “Fe”-doped bulk CuO using synchrotron radiation. From the absence of any strong new peaks at high pressure, it is evident that the secondary phases if present could be less than the level of detection. Cu2O, which is diamagnetic by nature, was also doped with 1% of “Fe” and was found to show paramagnetic behavior in contrast to the “Fe” doped CuO. Hence the possibility of intrinsic magnetization of “Fe”-doped CuO apart from the secondary phases is discussed based on the magnetization and charge state of “Fe” and the host into which it is substituted.

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Section: High-pressure X-ray Diffraction Using Synchrotron Radiationmentioning

confidence: 89%

Section: High-pressure X-ray Diffraction Using Synchrotron Radiationmentioning

confidence: 99%

Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Joseph

Venkateswaran

Vennila

2010

Advances in Materials Science and Engineering

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“…Although these methods have been used quite successfully for simple binary materials, 72,73 accurate band offsets for ternary delafossites do not seem possible using this method. As delafossites and Cu I oxides, in general, are known to be polaronic, [69][70][71][90][91][92][93][94][95][96][97][98][99][100] it is expected that the Cu-Cu distances should play a part in any conductivity, as holes are expected to hop from Cu to Cu. 71 The Cu-Cu distance ͑equal to the a / b lattice constant͒ is determined by the size of the M III ion, which suggests that the conductivity will increase as the size of the M III ion decreases.…”

Section: Discussionmentioning

confidence: 99%

Understanding conductivity anomalies in CuI-based delafossite transparent conducting oxides: Theoretical insights

Scanlon

Godinho²,

Morgan³

et al. 2010

The Journal of Chemical Physics

107

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The Cu I -based delafossite structure, Cu I M III O 2 , can accommodate a wide range of rare earth and transition metal cations on the M III site. Substitutional doping of divalent ions for these trivalent metals is known to produce higher p-type conductivity than that occurring in the undoped materials. However, an explanation of the conductivity anomalies observed in these p-type materials, as the trivalent metal is varied, is still lacking. In this article, we examine the electronic structure of Cu I M III O 2 ͑M III =Al,Cr,Sc,Y͒ using density functional theory corrected for on-site Coulomb interactions in strongly correlated systems ͑GGA+ U͒ and discuss the unusual experimental trends. The importance of covalent interactions between the M III cation and oxygen for improving conductivity in the delafossite structure is highlighted, with the covalency trends found to perfectly match the conductivity trends. We also show that calculating the natural band offsets and the effective masses of the valence band maxima is not an ideal method to classify the conduction properties of these ternary materials.

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“…Delafossites and Cu I oxides in general are considered to be polaronic, [53][54][55][56]58,70,96,[99][100][101][102][103][104][105][106] and as such it is expected that the CuCu distances should play a part in any conductivity, with holes expected to hop from Cu to Cu. 58 The Cu-Cu distance (equal to the a/b lattice constant) is determined by the size of the M III ion, which suggests that the conductivity will increase as the size of the M III ion decreases.…”

Section: Discussionmentioning

confidence: 99%

Understanding the p-Type Conduction Properties of the Transparent Conducting Oxide CuBO₂: A Density Functional Theory Analysis

2009

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CuCrO 2 is the most promising Cu-based delafossite for p-type optoelectronic devices. Despite this, little is known about the p-type conduction mechanism of this material, with both Cu I /Cu II and Cr III /Cr IV hole mechanisms being proposed. In this article we examine the electronic structure, thermodynamic stability and the p-type defect chemistry of this ternary compound using density functional theory with three different approaches to the exchange and correlation; the generalized-gradient-approximation of Perdew, Burke and Ernzerhof (PBE), PBE with an additional correction for on-site Coulombic interactions (PBE + U) and the nonlocal, screened-exchange hybrid functional HSE06. The fundamental band gap of CuCrO 2 is demonstrated to be indirect in nature. Under all growth conditions, the dominant intrinsic p-type defect will be the Cu vacancy, with hole formation centered solely on the Cu sublattice. Mg doping is found to be significantly lower in energy than intrinsic defect formation, explaining the large increases in conductivity seen experimentally. Cu-rich/Cr-poor growth conditions are found to be optimal for both intrinsic and extrinsic (Mg doping) defect formation, and should be adopted to maximize performance.

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High-pressure electrical conductivity measurements in the copper oxides

Cited by 49 publications

References 14 publications

Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Understanding conductivity anomalies in CuI-based delafossite transparent conducting oxides: Theoretical insights

Understanding the p-Type Conduction Properties of the Transparent Conducting Oxide CuBO₂: A Density Functional Theory Analysis

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High-pressure electrical conductivity measurements in the copper oxides

Cited by 49 publications

References 14 publications

Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Understanding conductivity anomalies in CuI-based delafossite transparent conducting oxides: Theoretical insights

Understanding the p-Type Conduction Properties of the Transparent Conducting Oxide CuBO2: A Density Functional Theory Analysis

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Understanding the p-Type Conduction Properties of the Transparent Conducting Oxide CuBO₂: A Density Functional Theory Analysis