Presence of Peierls pairing and absence of insulator-to-metal transition in VO₂ (A): a structure–property relationship study

Abstract

Layered vanadium oxides have been extensively explored due to their interesting metal-insulator transitions and energy conversion/storage applications. In the present study, we have successfully synthesized VO (A) polymorph powder samples by a single-step hydrothermal synthesis process and consolidated them using spark plasma sintering. The structural and electronic properties of VO (A) are measured over a large temperature range from liquid helium, across the structural transition (400-440 K) and up to 500 K. The structural analysis around this transition reveals an antiferrodistorsive to partially ferrodistorsive ordering upon cooling. It is followed by a progressive antiferromagnetic spin pairing which fully settles at about 150 K. The transport measurements show that, in contrast to the rutile archetype VO (R/M1), the structural transition comes with a transition from semiconductor to band-type insulator. Under these circumstances, we propose a scenario with a high temperature antiferrodistorsive paramagnetic semiconducting phase, followed by an intermediate regime with a partially ferrodistorsive paramagnetic semiconducting phase, and finally a low temperature partially ferrodistorsive antiferromagnetic band insulator phase with a possible V-V Peierls-type pairing.

Toward Room-Temperature Thermochromism of VO2 by Nb Doping: Magnetic Investigations

“…To explain the low- T susceptibility plateau, the formation of covalent V–V pairs was suggested . After this stable value in the temperature range of 300–150 K, the magnetic susceptibility shows a rapid increase below 150 K, which was interpreted by the presence of traces of unpaired V 4+ spins probably due to defaults (lattice defects) in the structure …”

“…34 After this stable value in the temperature range of 300−150 K, the magnetic susceptibility shows a rapid increase below 150 K, which was interpreted by the presence of traces of unpaired V 4+ spins probably due to defaults (lattice defects) in the structure. 35 First, we discuss the variation of the Pauli plateau values in the high-T range for different samples. The fits of the Pauli magnetic part were made by refining two key variables: the Fermi energy (E F 0 ) of the compound and the number of charge carriers per mol (N p ) using the following equations,…”

Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows

“…Meanwhile, the transformation from VO 2 (A) to VO 2 (M) face the same issues as that of VO 2 (B), such as the high annealing temperature and resultant coarsening of VO 2 (M). Researches on VO 2 (A) are mainly concentrate on its structure phase transition and electrochemical properties …”

Combined Effect of Temperature Induced Strain and Oxygen Vacancy on Metal‐Insulator Transition of VO2 Colloidal Particles

“…The thermochromic phase transition temperature (T C; T C-heat for insulator to metal, IMT and T C-cool for the metal-insulator transition, MIT) of as-synthesized VO 2 (A) and annealed samples were investigated by differential scanning calorimetry (DSC) (Figure 6a). When the phase transition of VO 2 (A) occurs, it exhibits noticeable endothermic peak at 161 °C due to conversion from low temperature phase (VO 2 (A) LTP -P4/ncc, 130) to high temperature phase (VO 2 (A) HTP -I4/m, 87), [59,60] but no reversible transition in the cooling cycle. [60] However, for the sample annealed at 550 °C (Figure 6b, Figure S4a, Supporting Information), the endothermic transition temperature (T C1-heat ) was centered at ≈66.8 °C with exothermic peak found at 58 °C (T C1-cool ).…”