Short-range ordering of vacancies in TiO at 1323 K

Self Cite

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.

Section: Local Ordersupporting

confidence: 55%

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

Morinaga¹,

Cohen²

1979

Self Cite

“…Hayakawa & Cohen, 1975) and in such volumes the variations in the scattering-factor terms in Tables 3 and 4 are not sufficiently small to utilize this procedure. The least-squares procedure has been used successfully in previous studies of oxides (Terauchi & Cohen, 1979;. The region of measurement in this study is illustrated in Fig.…”

Section: + H ~ R~(h) + H~ R(h) + H] Gz(h)mentioning

confidence: 98%

X-ray diffraction study of Zr(Ca,Y)O2−x. II. Local ionic arrangements

Morinaga¹,

Cohen²,

Faber³

1980

Self Cite

Above the 1300 K transition and in the defect fluorite phase, there is diffuse X-ray scattering which is similar for both Ca-and Y-stabilized zirconias. This is largely due to ionic displacements from the average structure, principally oxygen ions displaced locally in (100) directions. It has been proposed that some of this scattering is due to fine precipitates of ZrCaaO 9 or ZrY409. The quantitative analysis of this diffuse scattering reported here does indeed indicate some similarities to this phase; in particular the stabilizing __ ions form rods in the (332) directions similar to those in the precipitate. However, in this compound the stabilizing ion is a second neighbor to an oxygen-ion vacancy, whereas the present results indicate that these tend to be first neighbors. This is the first direct evidence for this association in these materials. This probably occurs to reduce local distortions and to provide local charge balance. It is concluded that the diffuse intensity is from locally ordered regions, not precipitates.

“…A more recent example discussing stacking faults can be found in Bü rgi et al (2005). A combination of first-order diffuse scattering due to chemical SRO and the resulting size effect has been applied to metal alloys (Terauchi & Cohen, 1979;Morinaga & Cohen, 1979;Morinaga et al, 1980). A more recent example can be found in Schö nfeld et al (2011).…”

Section: Introductionmentioning

confidence: 99%

Diffuse single-crystal scattering corrected for molecular form factor effects

Schmidt

Neder

2017