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The spatial organization of metal oxide nanoparticles represents an important factor in the chemical utilization of resulting structures. For the production of networks that are composed of metal oxide nanoparticle chains, we dispersed vapor phase-grown TiO2 and ZnO nanoparticles homogeneously in an aqueous polyvinyl alcohol solution. After electrospinning, we analyzed the sizes and diameters of the compositionally homogeneous electrospun fibers and discussed the size distribution and morphology of the nanoparticles inside. Calcination-induced polymer removal gives rise to self-supported nanoparticle-based nanofibers. Particle coarsening by a factor of ~ 2 for TiO2 and ~ 3 for ZnO nanoparticles is observed. Graphical abstract

Nanostructured segregates of alkaline earth oxides exhibit bright photoluminescence emission and great potential as components of earth-abundant inorganic phosphors. We evaluated segregation engineering of Ca 2+ - and Ba 2+ -admixtures in sintered MgO nanocube-derived compacts. Compaction and sintering transform the nanoparticle agglomerates into ceramics with residual porosities of Φ = 24–28%. Size mismatch drives admixture segregation into the intergranular region, where they form thin metal oxide films and inclusions decorating grain boundaries and pores. An important trend in the median grain size evolution of the sintered bodies with d Ca(10 at. %) = 90 nm < d Ba(1 at. %) = 160 nm < d MgO = 250 nm ∼ d Ca(1 at. %) = 280 nm < d Ba(10 at. %) = 870 nm is rationalized by segregation and interface energies, barriers for ion diffusion, admixture concentration, and the increasing surface basicity of the grains during processing. We outline the potential of admixtures on interface engineering in MgO nanocrystal-derived ceramics and demonstrate that in the sintered compacts, the photoluminescence emission originating from the grain surfaces is retained. Interior parts of the ceramic, which are accessible to molecules from the gas phase, contribute with oxygen partial pressure-dependent intensities to light emission.

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Ion exsolution can be instrumental to engineer intergranular regions inside ceramic microstructures. BaO admixtures that were trapped inside nanometer‐sized MgO grains during gas phase synthesis undergo annealing‐induced exsolution to generate photoluminescent surface and interface structures. During their segregation from the bulk into the grain interfaces, the BaO admixtures impact grain coarsening and powder densification, effects that were compared for the first time using an integrated characterization approach. For the characterization of the different stages the materials adopt between powder synthesis and compact annealing, spectroscopy measurements (UV–Vis diffuse reflectance, cathodo‐ and photoluminescence [PL]) were complemented by an in‐depth structure characterization (density measurements, X‐ray diffraction [XRD], and electron microscopy). Depending on the Ba2+ concentration, isolated impurity ions either become part of low‐coordinated surface structures of the MgO grains where they give rise to a characteristic bright PL emission profile around λ = 500 nm, or they aggregate to form nanocrystalline BaO segregates at the inner pore surfaces to produce an emission feature centered at λ = 460 nm. Both types of PL emission sites exhibit O2 gas adsorption‐dependent PL emission properties that are reversible with respect to its pressure. The here‐reported distribution of BaO segregates between the intergranular region and the free pore surfaces inside the MgO‐based compacts underlines that solid‐based exsolution strategies are well suited to stabilize nanometer‐sized segregates of metal oxides that otherwise would coalesce and grow in size beyond the nanoscale.