On the nucleation and paracrystal interspacing of Zr-doped Co3−δO4

Abstract

A paracrystalline array of defect clusters was shown to form in Zr-doped Co 3−δ O 4 spinel in the ZrO 2 /Co 1−x O composites while prepared by a sintering route at 1650• C in air. Analytical electron microscopic observations indicated the spinel precipitate and its paracrystal predominantly formed at the ZrO 2 /Co 1−x O interface and the cleavages/dislocations of the Co 1−x O host. Defect chemistry consideration suggests the paracrystal is due to the assembly of charge-and volume-compensating defects of the 4:1 type with four octahedral vacant sites surrounding one Co 3+ -filled tetrahedral interstitial site. The interspacing of such defect clusters is 4.9 times the lattice spacing of the average spinel structure of Zr-doped Co 3−δ O 4 . This spacing between defect clusters is about 0.98 times that of our previously studied undoped Co 3−δ O 4 . There is much larger (3.4 times difference) paracrystalline spacing for Zr-doped Co 3−δ O 4 than its parent phase of Zr-doped Co 1−x O.

Laser ablation condensation and phase change of Ni1−xCoxO nanoparticles

“…It is noteworthy that the interspacing of the paracrystalline defect clusters in the present Co 3Àd O 4 condensates with negligible dissolution of NiO is nearly the same as that in the bulk of Co 3Àd O 4 spinel (5.0 times that of the average spinel cell dimension) [9], but significantly smaller than that of Zr-doped Co 3Àd O 4 spinel (4.9 times that of the average spinel cell dimension) [10]. In fact, the d value of Zr-doped Co 3Àd O 4 [10]) was estimated to be 2% larger than undoped Co 3Àd O 4 (d ¼ 0.0002) [9]. The extra cobalt vacancies and Co 3+ interstitials in Zr-doped Co 3Àd O 4 may thus form extra 4:1 defect clusters for a smaller interspacing.…”

“…The extra Co 3+ deviating from stoichiometric spinel, as denoted by d in the formula Co 3 À d O 4 , may occupy both tetrahedral A sites and octahedral B sites at high temperatures as the case of so-called disordered spinel above 1150 K [27]. It is noteworthy that the interspacing of the paracrystalline defect clusters in the present Co 3Àd O 4 condensates with negligible dissolution of NiO is nearly the same as that in the bulk of Co 3Àd O 4 spinel (5.0 times that of the average spinel cell dimension) [9], but significantly smaller than that of Zr-doped Co 3Àd O 4 spinel (4.9 times that of the average spinel cell dimension) [10]. In fact, the d value of Zr-doped Co 3Àd O 4 [10]) was estimated to be 2% larger than undoped Co 3Àd O 4 (d ¼ 0.0002) [9].…”

“…Such distribution of defect clusters typically occurred for 3d transition metal cubicclose-packed (ccp) monoxide with varied extent of nonstoichiometry such as Fe 1Àx O [3] and doping of aliovalent and/or volume-mismatch cations such as (Y, Zr)-codoped Ni 1Àx O [4]; Zr-doped Ni 1Àx O [5]; Ca-doped Ni 1Àx O [6]; (Zr, Y)-codoped Co 1Àx O [7,8]. Paracrystals were also reported for Co 3Àd O 4 spinel [9] and Zr-doped Co 3Àd O 4 spinel [10].…”

On the transformation pathways of alpha-PbO2-type TiO2 at the twin boundary of rutile bicrystals and the origin of rutile bicrystals

“…The satellite diffractions of (202) and (112) in Fig. 5a can possibly be attributed to such misregistered atoms/clusters analogous to defect clustering of paracrystals in other transition metal oxides (Li & Shen, 2004 and literature cited therein). SAED pattern indicated that the diffractions of [ -PbO 2 -type TiO 2 slab and the twin spots of rutile bicrystals (Fig.…”

Soft X-ray absorption spectroscopy study of (Ba0.5Sr0.5) (Co0.8Fe0.2)1−хNbхO3−δ with different content of Nb (5%–20%)

“…In Co3O4 which has spinel-type structure cobalt ions exist in two different oxidation states, Co 2+ and Co 3+ . Co atoms can, therefore, occupy both octahedrally coordinated sites (16 sites for Co 3+ ) and tetrahedrally coordinated sites (8 sites for Co 2+ ) with the ratio 2:1 [27]. In Co3O4, the tetrahedral sites are occupied by Co 2+ with high-spin state configuration e 4 gt 3…”