Preparation, Structure Evolution, and Metal-Insulator Transition of Na xRhO2 Crystals (0.25 ≤ x ≤ 1)

Bin-Bin Zhang; Cong Wang; Song-Tao Dong; Yang-Yang Lv; Lunyong Zhang; Yadong Xu; Y B Chen; Jian Zhou; Shu-Hua Yao; Yan-Feng Chen

doi:10.1021/acs.inorgchem.7b03110

Preparation, Structure Evolution, and Metal-Insulator Transition of Na _xRhO₂ Crystals (0.25 ≤ x ≤ 1)

Inorg Chem. 2018 Mar 5;57(5):2730-2735. doi: 10.1021/acs.inorgchem.7b03110. Epub 2018 Feb 15.

Authors

Bin-Bin Zhang^{1

2}, Cong Wang¹, Song-Tao Dong³, Yang-Yang Lv¹, Lunyong Zhang^{4

5}, Yadong Xu², Y B Chen⁶, Jian Zhou^{1

7}, Shu-Hua Yao^{1

7}, Yan-Feng Chen^{1

7}

Affiliations

¹ National Laboratory of Solid State Microstructures Department of Materials Science and Engineering , Nanjing University , Nanjing 210093 , People's Republic of China.
² Key Laboratory of Radiation Detection Materials and Devices, Ministry of Industry and Information Technology, School of Materials Science and Engineering State Key Laboratory of Solidification Processing , Northwestern Polytechnical University , Xi'an , Shaanxi 710072 , People's Republic of China.
³ Institute of Materials Science and Engineering , Jiangsu University of Science and Technology , Zhenjiang 212003 , People's Republic of China.
⁴ Max Planck Postech Center for Complex Phase Materials, Max Planck Postech/Korea Research Initiative (MPK) , Gyeongbuk 376-73 , Korea.
⁵ Max Planck Institute for Chemical Physics of Solids , Nöthnitzerstr. , Dresden 40 01187 , Germany.
⁶ National Laboratory of Solid State Microstructures & Department of Physics , Nanjing University , Nanjing 210093 , People's Republic of China.
⁷ Collaborative Innovation Center of Advanced Microstructure , Nanjing University , Nanjing 210093 , People's Republic of China.

PMID: 29446937
DOI: 10.1021/acs.inorgchem.7b03110

Abstract

The triangular lattice Na _xRhO₂ contains a 4d Rh element with large spin-orbit coupling, and the electron-electron correlation effect is expected to have some novel physical properties. Here we report NaRhO₂ crystal growth by Na₂CO₃ vapor growth and a series of Na _xRhO₂ (0.25 ≤ x ≤ 1) crystals prepared using the chemical desodiation method. Na _xRhO₂ reveals a layer structure with the space group R3̅ m, and the lattice parameter a evolves from 3.09 to 3.03 Å and c from 15.54 to 15.62 Å when x decreases from 1.0 to 0.2. Decreasing potassium concentration leads to a contraction of the RhO₆ octahedral layers, which may be attributed to a higher covalency of Rh-O bonds. More important, the metal-insulator transition in Na _xRhO₂ was observed in resistivity along the ab plane. The conducting mechanism of Na _xRhO₂ is strongly dependent on x. Two-dimensional variable range hopping (VRH) mechanisms (0.67 ≤ x ≤ 1) and metallic behaviors (0.42 and 0.47) are observed in temperature-dependent resistivity. The origin of this metal-insulator transition was discussed on the basis of the Ioffe-Regel criterion. Our work demonstrates the strong correlation between sodium concentration and physical properties of Na _xRhO₂.