Single oxygen-deficient

Above 1127°C, a single oxygen-rich non-stoichiometric phase of UO2 is found with formula U02+, ranging from UO2 to U02.25- Unlike FeO, where a metal-deficient oxide was achieved through cation vacancies, in this example the metal-deficiency arises from interstitial anions. 

In general, it is accepted that recombination of electrons and holes, trapping of electrons by oxygen deficiency sites and a low mobility of the holes, cause a low conductivity and accordingly a low photoresponse for hematite. Electron mobility in the range 0.01 [60] to 0.1 cm2/V-s [17] has been reported. In the latter case, it was found that the electron mobility was independent of donor concentration. More recently, an electron mobility of about 0.1 cm2/V-s has been measured with doped single crystals and the mobility was also here independent of donor concentration [5]. A diffusion length of holes has been determined to be only of 2-4 nm [6], which is about 100 times lower than many other (III-V) oxides. 

The preparation of pure, single-phase oxides of true stoichiometry is often difficult, sometimes impossible. FeO and MnOg are examples, the former being always metal-deficicnt, the latter always oxygen-deficient (p. 429, 484). 

Description. Every cell in the body requires iron for a variety of functions. This versatile mineral is involved in oxygen transport (hemoglobin) and storage (myoglobin), is required by enzymes that produce energy for the cell, and it plays an important role in the function of the immune and central nervous systems. Iron is required in relatively high doses to maintain proper nutrition. Of aU the nutrients, the allowance for iron is the most difficult to obtain from dietary sources, aud therefore is the most common single micronutrient deficiency in the world. ... 

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