Apparent crystallite domain size growth in metal oxide nanocrystal ensembles: The importance of surface reactivity of powders for processing

Segregation Engineering in MgO Nanoparticle-Derived Ceramics: The Impact of Calcium and Barium Admixtures on the Microstructure and Light Emission Properties

“…The XRD patterns related to the Ba 2+ -doped MgO samples indicate the presence of multiple crystallographic phases. 43 , 44 The evidence for barium peroxide and carbonate reflects the increased surface basicity of Ba 2+ -segregates. 44 − 47…”

“…BaO moieties at the surface of less reactive grains such as MgO instantaneously react with water to form surface hydroxides. 44 Additionally adsorbed water forming thin films that cover these highly dispersed structures act as a two-dimensional solvent, facilitates mass transport, and acts as a sintering aid. 56 , 57 Thus, the higher the surface basicity and reactivity of the nanocrystalline starting material, the higher is the uptake of water from the ambient.…”

“…There is an increase in surface basicity of the grains induced by the Ca 2+ –O 2– or Ba 2+ –O 2– moieties in the grain surfaces. , This, in turn, promotes the adsorption of H 2 O and/or CO 2 molecules during material compaction and handling in air. BaO moieties at the surface of less reactive grains such as MgO instantaneously react with water to form surface hydroxides . Additionally adsorbed water forming thin films that cover these highly dispersed structures act as a two-dimensional solvent, facilitates mass transport, and acts as a sintering aid. , Thus, the higher the surface basicity and reactivity of the nanocrystalline starting material, the higher is the uptake of water from the ambient.…”

“…The XRD patterns related to the Ba 2+ -doped MgO samples indicate the presence of multiple crystallographic phases. 43,44 The evidence for barium peroxide and carbonate reflects the increased surface basicity of Ba 2+ -segregates. 44−47 SEM measurements on Ca 2+ -and Ba 2+ -doped ceramic fracture surfaces (Figure 3) were performed to assess grain sizes and morphologies and to compare these observations with ceramics derived from MgO nanocube powders without admixtures.…”

Conversion of MgO nanocrystal surfaces into ceramic interfaces: Exsolution of BaO as photoluminescent interface probes

“…From a chemical perspective, highly dispersed BaO exhibits a remarkable surface basicity. When accessible to gaseous or condensed water from the atmosphere, such surface decorations can induce substantial reactivity changes at room temperature, which were found to directly affect particle size distribution (PSD) and morphology 20 . Based on a previous analysis of the optical properties of Ba‐doped MgO nanoparticle powders, we now use these impurities as optical probes to track the transformation of free nanoparticle surfaces into interfaces that emerge upon powder compaction and sintering in nano‐ or microcrystalline ceramics.…”