Defect clusters and precipitation/oxidation of MgO–Co1−xO solid solution

Cu2O(110) formation on Co3O4(110) induced by copper impurity segregation

“…Several possibilities for the composition of this layer can be ruled out based on AES/XPS data and by comparison of the overlayer LEED pattern to the twodimensional LEED patterns determined from kinematic calculations of other potential overlayer structures [48]. Surface structures considered include the impurity surface forming an incomplete Type B spinel termination layer [49], a mixed-metal copper cobalt oxide spinel layer [3,[11][12][13][14], a mixed-metal copper cobalt oxide solid solution [50], or a phase-separation copper oxide layer on the spinel surface [14,27,28]. The O/Co surface concentration ratio determined from AES and XPS data indicates a reduced surface, with insuffi cient oxygen to form a spinel as the majority species.…”

“…Co 3 O 4 is antiferromagnetic in which each Co 2+ cation is surrounded by four nearest neighbors with opposite spin [23] and it is a p-type semiconductor with a band gap of about 2.2 eV [24]. Dopants or impurities can have a substantial effect on electronic and magnetic properties [10], [25] and [26] and they can affect the stability of the spinel structure [12,27]. Transition metals that substitute for the cobalt in the M 2+ M 2 3+ O 4 spinel (M 2+ , M 3+ = cobalt or dopant metal) have been observed to change the distribution of cation oxidation states, creating an inverted or partially inverted spinel structure in which the M 3+ cations now occupy both octahedral and tetrahedral sites and at least some of the M 2+ are found in octahedral sites [12,[15][16][17].…”

Spinel precipitation in Sn4+-doped Co1−xO polycrystals with dispersed Co2+xSn1−xO4 particles

“…zone is common for nonstoichiometric transition metal oxides of rock salt-type structure such as wustite Fe 1Àx O [5,6], Ni 1Àx O dissolved with Zr 4+ [7] or Ca 2+ [8], and Co 1Àx O dissolved with Zr 4+ [9] or [ ( F i g . _ 9 ) T D $ F I G ] Mg 2+ [10]. However, the paracrystalline distribution of 4:1 defect clusters is vague in Sn 4+ -doped Co 1Àx O in comparison with the significant paracrystals in Co 1Àx O dissolved with Zr 4+ [9] or Mg 2+ [10].…”

“…_ 9 ) T D $ F I G ] Mg 2+ [10]. However, the paracrystalline distribution of 4:1 defect clusters is vague in Sn 4+ -doped Co 1Àx O in comparison with the significant paracrystals in Co 1Àx O dissolved with Zr 4+ [9] or Mg 2+ [10]. Apparently, the driving force to precipitate directly the Co 2+x Sn 1Àx O 4 spinel is strong enough to bypass the metastable formation of G.P.…”

“…13:4, 16:5 and form a paracrystal [1,2]), which order further into Fe 3 O 4 spinel or other ordered phases: p 00 and p 000 [5,6]. The experimental results of Ni 1Àx O dissolved with Zr 4+ [7] or Ca 2+ [8], Co 1Àx O dissolved with Zr 4+ [9] or Mg 2+ [10] and CaO dissolved with Ni 2+ [11] or Co 2+ [12], further showed that paracrystalline interspacing of defect clusters of rock salt-type oxides could be tailored by doping specific cations.…”