The defect structure of VO_x. II. Local ionic arrangements in the disordered phase

Abstract

In VO x (0.8 < x < 1.3), there are large numbers of cation and anion vacancies and interstitial vanadium ions. To determine the local arrangements of these defects, X-ray diffuse scattering was measured in absolute units with single crystals of VO x (x = 0.89, 1.17 and 1.28). For x > 1, the interstitials are present near vacancy clusters, similar to the defect arrays found in the semiconductor FexO. For x < 1, there are few interstitials, but an increased concentration of anion vacancies. The anion and cation vacancies are arranged (so as to minimize the electrostatic energy) in rows along (110) directions with alternating vacancy-rich and vacancy-deficient { 111 } layers. Some portions of this vacancy arrangement resemble that found in metallic TiOx. VO x behaves like a semimetal for x < 1, but a semiconductor for x > 1, and the present results, when compared to the defect structures in TiOx and FexO, show that the nature of the bonding between cations and anions controlling the conduction mechanism is reflected in the defect structure.

Electrical and optical properties of sputtered amorphous vanadium oxide thin films

“…4,5 For the last 20 years VO x has been used as the active material in uncooled infrared imaging detectors operating in the pulsed bias readout mode [1][2][3] and have been contradictorily reported as having amorphous 6 and polycrystalline 7 structure, with nonstoichiometries 8 and mixed-oxides. 9 Recent evidence has indicated that the true nature of the microstructure of VO x for microbolometer applications is a composite of rock-salt face centered cubic (fcc) vanadium monoxide phase [10][11][12][13][14] nanocrystallites, where the oxygen content "x" in VO x can vary from 0.8 < x < 1.3, and an amorphous component present between the crystallites. Similarly, room-temperature monoclinic, high-temperature (>68 C) rutile vanadium dioxide, used for its relatively sharp temperature-dependent shift in resistivity and transmittance denoted as the metal-to-semiconductor transition, may contain higher x amorphous material between crystallites present in thin film forms of interest for new "phase change" applications.…”

Metal Vacancy Ordering in an Antiperovskite Resulting in Two Modifications of Fe2SeO

“…The fact that vacancies exist on possible Fe sites only underlines this possibility, as the best O 2À ion conductors, for example, d-Bi 2 O 3 [21,22] and yttriastabilized zirconia (YSZ), [23,24] have oxygen-deficient fluorite structures. Furthermore, the tetrahedral slabs in the oxygenion-conducting brownmillerites, [25,26] for example, Ca 2 FeAlO 5 , even have a close anti-type structural relation with the title compounds.…”

Direct and Indirect Methods of the Analysis of Interatomic Interaction and Kinetics of a Relaxation of the Short-Range Order in Close-Packed Substitutional (Interstitial) Solid Solutions

“…Розвиток методики дифузного розсіяння дозволяє дослідити також тверді роз-чини втілення (див. бібліографію в [128,156,164,166,224,225,[238][239][240][241][242][243][244][245][246][247][248]) та більш складні системи, що містять декілька нееквівалентних вузлів в елементарній комірці [44][45][46], і навіть розчини органічних спо-лук [47,93].…”