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Positron and positronium annihilation as probes to identify cation substitution effects in CoCr_xFe_(2-x)O_4

机译：正电子and灭作为探针来确定CoCr_xFe_（2-x）O_4中的阳离子取代作用

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CoCr_xFe_(2-x)O_4 samples with several values of x between 0.0 and 2.0 were prepared by air oxidation of aqueous suspension containing Co~(2+), Cr~(3+) and Fe~(3+)ions and characterized by X-ray diffraction. Positron lifetime and coincidence Doppler broadening (CDB) measurements were carried out to identify the defects at the different stages of substitution. Initially the vacancy-type defects at the A-sites (tetrahedral) trapped positrons but, with the substitution of Fe~(3+)by Cr3* ions in low concentrations (x ≤ 0.7), positrons are trapped by defects at the B-sites (octahedral). The cationic distributions at B-sites are stoichiometry-dependent and, till x = 0.7, the deficiency of Fe~(3+)(B) ions was compensated by interchange of Fe~(3+)(A) ions with Co~(2+)(B) ions. Between x = 0.9 and 1.7, the substitution resulted in continued decrease of Fe~(3+)(B) ions and the structure got fully transformed into a normal spinel configuration during x = 1.8 to 2.0.
机译：通过空气氧化含有Co〜（2 +），Cr〜（3+）和Fe〜（3+）离子的水悬浮液，制备了x值在0.0到2.0之间的CoCr_xFe_（2-x）O_4样品，并进行了表征X射线衍射。进行了正电子寿命和巧合多普勒加宽（CDB）测量，以识别替换不同阶段的缺陷。最初，A位（四面体）俘获的正电子为空位型缺陷，但是当Fe〜（3+）被低浓度（x≤0.7）的Cr3 *离子取代时，正电子被B-处的缺陷俘获。网站（八面体）。 B位的阳离子分布与化学计量有关，直到x = 0.7为止，Fe〜（3 +）（A）离子与Co〜（ 2 +）（B）离子。在x = 0.9到1.7之间，取代导致Fe〜（3 +）（B）离子的持续减少，并且在x = 1.8到2.0时，结构完全转变为正常的尖晶石构型。

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