Annealing-Induced {011}-Specific Cyclic Twins in Tetragonal Zirconia Nanoparticles

Abstract

Zirconia (ZrO 2 ) nanocrystals with average size of 4 nm are fabricated by oxidation of the nonstoichiometric ZrC 0.6 with ordered carbon vacancies at 450 °C under atmosphere. The nanocrystals are predominantly tetragonal (t) phase and spherical in shape, and their exposed surfaces are constructed by the {011} and {001} facets. After annealing at 700 °C under atmosphere, the coalescence of adjacent t-ZrO 2 nanocrystals is observed, and most of the annealed t-ZrO 2 nanoparticles are found to exhibit the {011}-specific twins. The dominant cyclic twins as well as a small number of the single and lamellar twins are recognized in the twinned nanoparticles. The cyclic-twinned nanoparticles are identified to have the 5-fold symmetry of either decahedron or icosahedron. In contrast to the single and lamellar twins which are formed via the coalescence of adjacent nanocrystals on the well-developed {011} surfaces, the cyclic-twinned nanoparticles are developed from the coalescence on the disoriented contact surfaces, in which the emission of partial dislocations and induced deformation are recognized to play the key role.

Beyond Simple Crystal Systems: Identifying Twinning in Body-Centered Tetragonal Nanoparticles

“…, Figure b), so again care must be taken to examine the NP along several directions. Lastly, there are no reports, to our knowledge, of icosahedra of In, but they are likely possible, similarly to those observed in other tetragonal structures, and perhaps have been observed but confused with rounded single crystals.…”

Assembly of monoclinic ZrO2nanorods: formation mechanism and crystal phase control

“…It is generally proposed that the martensitic transformation from t-ZrO 2 to m-ZrO 2 nanoparticles was controlled by the nucleation kinetics and accompanied by the formation of twinning structures on an individual nanoparticle. 15,[40][41][42] Under the current hydrothermal conditions, however, such a kind of twinning structure was not observed. It is most likely that the higher concentration of ammonia caused very fast hydrolysis of ZrO 2+ species and produced larger amounts of crystallite nuclei before the hydrothermal treatment.…”

Olivine Crystal Structure-Directed Twinning in Iron Germanium Sulfide (Fe2GeS4) Nanoparticles

“…However, this would rely on the ability to characterize the atomic structure of the twin boundaries unambiguously in the NPs. High-resolution electron microscopy techniques can provide powerful methods to understand the arrangement of atoms at defect sites, but very thin samples lend themselves best to these methods, including two-dimensional materials ( i.e ., MoS 2 ) and smaller NPs . Because the width of the Fe 2 GeS 4 NPs can be up to ∼200 nm, it is difficult to detect the exact atomic composition of the twin boundaries.…”

“…High-resolution electron microscopy techniques can provide powerful methods to understand the arrangement of atoms at defect sites, but very thin samples lend themselves best to these methods, including two-dimensional materials (i.e., MoS 2 ) 23 and smaller NPs. 25 Because the width of the Fe 2 GeS 4 NPs can be up to ∼200 nm, it is difficult to detect the exact atomic composition of the twin boundaries. Shorter growth times were explored, but sufficiently small particles could not be attained, and at very early stages of growth, the majority of the product was amorphous.…”

“…Crystal defects, including twin boundaries, play a significant role in material properties and performance; however, limited knowledge exists about the synthetic control required to controllably initiate twin formation in solution-based nanoparticle syntheses. The majority of reports examining the synthesis of twinned nanoparticles exist for unary compounds. − Fewer reports exist for binary compounds, and most feature nanowires − or 2D nanostructures , instead of NPs. − To the best of our knowledge, only two reports of ternary twinned NPs via solution-based synthesis exist, but neither form single-phase twinned particles. , This area of synthesis is highly challenging, because it is difficult to retain phase-purity while altering synthetic conditions to achieve twin and grain boundary control.…”