Electron–Proton Co‐doping‐Induced Metal–Insulator Transition in VO 2 Film via Surface Self‐Assembled l ‐Ascorbic Acid Molecules

Reducing phase transition temperature of vanadium dioxide by ascorbic acid

The phase transition of vanadium dioxide brings huge change in its optical property, which is well used in thermochromic window, fixed-temperature heat sensor, laser protection and other fields. Tunable phase transition temperature is one key for its wide applications. In this paper we verified a new simple method to reduce phase transition temperature. A coordination effect of ascorbic acid on VO2powder reduces its phase transition temperature to about 32 °C. This simple method offers a new efficient option to deal with VO2, which may dramatically promote the applications of VO2.

A Room-Temperature Verwey-type Transition in Iron Oxide, Fe5 O6

Functional oxides whose physicochemical properties may be reversibly changed at standard conditions are potential candidates for the use in next‐generation nanoelectronic devices. To date, vanadium dioxide (VO₂) is the only known simple transition‐metal oxide that demonstrates a near‐room‐temperature metal–insulator transition that may be used in such appliances. In this work, we synthesized and investigated the crystals of a novel mixed‐valent iron oxide with an unconventional Fe₅O₆ stoichiometry. Near 275 K, Fe₅O₆ undergoes a Verwey‐type charge‐ordering transition that is concurrent with a dimerization in the iron chains and a following formation of new Fe−Fe chemical bonds. This unique feature highlights Fe₅O₆ as a promising candidate for the use in innovative applications. We established that the minimal Fe−Fe distance in the octahedral chains is a key parameter that determines the type and temperature of charge ordering. This model provides new insights into charge‐ordering phenomena in transition‐metal oxides in general.