Inversion domain boundaries (IDB's) in ZnO ceramics, associated with Sb2O3 doping, have been characterized using a range of electron microscopy techniques. The IDB's lie primarily on basal planes, but frequently are stepped along prismatic planes. The basal IDB can be characterized as (i) an inversion that causes an antisite exchange of cations and anions across the boundary, (ii) an effective displacement of the sixfold screw axis in the wurtzite structure vectors by a translation of 1/3 and (iii) a displacement normal to the boundary. Significant Sb segregation is detected in the basal IDB segments in agreement with previous work, and in ceramics doped with Sb2O3 and Bi2O3. These IDB's contained both Sb and Bi, suggesting that while Bi does not participate in IDB nucleation, it resides in the boundary. Comparison of experimental and calculated HREM images suggests that the IDB is composed of a monolayer of Type I (111) zinc antimonate spinel, consisting of a single layer of octahedrally coordinated zinc and antimony cations.
Atomistic simulation calculations are used to predict the solution mechanisms and the defect cluster geometries of: M2+ dopant cations in Y2O3, M3+ dopant cations in CoO and M2+ dopant cations in SrTiO3. The interatomic potential parameters were derived by simultaneously fitting the properties of a range of mixed cation materials. The results suggest that although both solution enthalpies and cluster binding energies do scale with ionic radius, the relationships can be quite complex, materials specific and will not necessarily exhibit simple minima when the radius of the host cation equals the dopant cation, as described in previous studies.
The crystallization of MgO‐Al2O3‐SiO2‐ZrO2 glasses at 1000°C was studied. Isothermal heat treatments of a cordierite‐based glass (2MgO.2Al2O3.5SiO2= Mg2Al4Si5O18) with 7 wt% ZrO2 produced surface crystallization of α‐cordierite and tetragonal ZrO2 (t‐ZrO2). These phases advanced into the glass by cocrystallization of t‐ZrO2 rods in an α‐cordierite matrix with a well‐defined orientation relation. The t‐ZrO2 rods were unstable with respect to diffusional breakup (a Rayleigh instability) and decomposed into rows of aligned ellipsoidal and spheroidal particles. The t‐ZrO2 was very resistant to transformation to monoclinic symmetry. With a similar glass containing 15 wt% ZrO2, surface crystallization of α‐cordierite and t‐ZrO2 was accompanied by internal crystallization of t‐ZrO2 dendrites. Transformation of the dendrites to mono‐clinic symmetry was observed under some conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.