Synthesis, Spectroscopic Characterization, and Observation of Massive Metal—Insulator Transitions in Nanowires of a Nonstoichiometric Vanadium Oxide Bronze

Abstract

Metal-insulator transitions in strongly correlated materials, induced by varying either temperature or dopant concentration, remain a topic of enduring interest in solid-state chemistry and physics owing to their fundamental importance in answering longstanding questions regarding correlation effects. We note here the unprecedented observation of a four-orders-of-magnitude metal-insulator transition in single nanowires of delta-K(x)V(2)O(5), when temperature is varied, which thus represents a rare new addition to the pantheon of materials exhibiting pronounced metal-insulator transitions in proximity to room temperature.

Synthetic beta‐K0.33V2O5 Nanorods: A Metal–Insulator Transition in Vanadium Oxide Bronze

“…It is known that a mixed valence of V 4 + /V 5 + = 1:5 in beta-A 0.33 V 2 O 5 may trigger electronic instability at the Fermi level to induce electronic phase transition, similar to the reported beta-phase and delta-phase bronzes, [6,[20][21] thereby implying a possible MIT for the obtained beta-K 0.33 V 2 O 5 sample. It is known that a mixed valence of V 4 + /V 5 + = 1:5 in beta-A 0.33 V 2 O 5 may trigger electronic instability at the Fermi level to induce electronic phase transition, similar to the reported beta-phase and delta-phase bronzes, [6,[20][21] thereby implying a possible MIT for the obtained beta-K 0.33 V 2 O 5 sample.…”

Electronic Phase Transitions of δ-AgxV2O5 Nanowires: Interplay between Geometric and Electronic Structures

“…The Ag + ions reside between the infinite V 2 O 5 layers and are coordinated solely to oxygen atoms from the 2D framework and not to any additional water molecules, as observed for the hydrated δ-Ca x V 2 O 5 phase. 9,27,33 The Ag + ions are coordinated by seven oxide ions in a monocapped trigonal prismatic local coordination environment ( Figure 1c). …”

“…A wide range of electronic phase transitions has been manifested in vanadium oxide bronzes ranging from semiconductor−semiconductor transitions, metal−insulator transitions, and charge ordering to superconductivity. 9 (30) a Space group = C2/m, a = 11.7875 (1) For the latter compound, upon application of an external pressure, the semiconductor− semiconductor transition is suppressed and a superconducting phase is stabilized below T c = 12.5 K. 36,37 Indeed, the interplay between charge ordered and superconducting states has been a recurring theme for vanadium oxide bronzes as well. 12, 13 The inset to Figure 3 indicates a plot of current (I) versus voltage (V) measured for the pressed pellet at temperatures between 150 and 350 K. Upon examining the trace acquired at 150 K, with increasing voltage, an abrupt increase in current is observed at a threshold voltage of ca.…”

“…Thermally activated small polaron hopping (phonon assisted transport) is thought to be the primary mode for electron transfer on the insulating side of the Mott transition. 9,38,39 The pronounced change in the resistance and activation energy may indicate a suppressed metal−insulator transition where disorder precludes full realization of metallic conductivity. Alternatively, improved overlap between V 3d orbitals reduces the Mott−Hubbard gap, but a finite gap remains in the temperature range examined here.…”

Structure‐Induced Switching of the Band Gap, Charge Order, and Correlation Strength in Ternary Vanadium Oxide Bronzes

“…At the same time, this can lead to the creation of many unique V 2 O 5 bronzes (M x V 2 O 5 , M=Ca, Sr, K, Pb. ), which exhibit multiple charge‐ordered states, electronic correlation effects, and colossal metal to insulator transitions . The accessibility of multiple oxidation states of the V ions also makes these materials of significant interest in the creation of supercapacitors .…”