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This study investigated Lu doping of Ba0.5La0.5CoO3 and its influence on the exsolution of oxide nanoparticles (NPs). As a result of Lu doping, we observed the phase segregation into the main Ba0.4La0.6Co0.85Lu0.15O3 (BLCO–Lu) phase and the secondary Ba0.85La0.15Co0.75Lu0.25O3 (BCO–Lu) phase. We noticed the exsolution of BCO–Lu nanoparticles on the main BLCO–Lu phase. Moreover, the BLCO–Lu phase exsolved in the form of nanoparticles on the adjacent BCO–Lu grains. That shows that the phases are covered with mutually exsolved oxide NPs. In addition, trace amounts of the BaLuCo4O7 phase are detected. We noticed that the exsolved oxides even in the as-prepared sample were fine (average size of 18 nm), and well distributed with a dense population of NPs above 280 per 1 μm2. Furthermore, we showed that the size and shape of the exsolved oxide NPs can be controlled by varying the annealing temperature. For example, at 800 °C the exsolved oxides segregate and form two different shapes; spherical and cuboidal, with an average size of 31 nm and NP population of about 23 NPs per μm2. Meanwhile, with lowering the temperature to 400 °C the oxides form only spherical and quite evenly distributed NPs with the occurrence of 137 NPs per 1 μm2. The obtained results open the possibility of tailoring a novel, more catalytically active material for future applications in electrochemical devices. [ABSTRACT FROM AUTHOR]

Herein, we report the discovery of a toroidal inorganic cluster of zirconium(IV) oxysulfate of unprecedented size with the formula Zr70(SO4)58(O/OH)146⋅x(H2O) (Zr70), which displays different packing of ring units and thus several polymorphic crystal structures. The ring measures over 3 nm across, has an inner cavity of 1 nm and displays a pseudo‐10‐fold rotational symmetry of Zr6 octahedra bridged by an additional Zr in the outer rim of the ring. Depending on the co‐crystallizing species, the rings form various crystalline phases in which the torus units are connected in extended chain and network structures. One phase, in which the ring units are arranged in layers and form one‐dimensional channels, displays high permanent porosity (BET surface area: 241 m2 g−1), and thus demonstrates a functional property for potential use in, for example, adsorption or heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Direct evidence of N2 formation after annealing of (ZnO)1−x(GaN)x alloys was revealed. N2 was trapped by VZn+Ga-clusters, forming faceted voids along grain boundaries. This study shows that N–N bonding is a competitive path for nitrogen after annealing, in addition to the increasing Ga–N bonds, indicating that N in O substitution sites (NO) is not a stable configuration. [ABSTRACT FROM AUTHOR]

We apply inline electron holography to investigate the electrostatic potential across an individual BaZr0.9Y0.1O3 grain boundary. With holography, we measure a grain boundary potential of −1.3 V. Electron energy loss spectroscopy analyses indicate that barium vacancies at the grain boundary are the main contributors to the potential well in this sample. Furthermore, geometric phase analysis and density functional theory calculations suggest that reduced atomic density at the grain boundary also contributes to the experimentally measured potential well. [ABSTRACT FROM AUTHOR]

Defect-engineering of TiO2 can have a major impact on its photocatalytic properties for the degradation of persisting and non-biodegradable pollutants. Herein, a series of intrinsic and extrinsic defects are induced by post annealing of crystalline TiO2 under different reducing atmospheres. A detailed optoelectronic characterization sheds light on the key characteristics of the defect-engineered TiO2 nanopowders that are linked to the photocatalytic performance of the prepared photocatalysts. The photodegradation of a model dye, malachite green, as well as the inactivation of bacterial endospores of the Geobacillus stearothermophilus species were studied in the presence of the developed catalysts under visible light illumination. Our results indicate that a combination of certain defects is necessary for the improvement of the photocatalytic process for water purification and disinfection under visible light. [ABSTRACT FROM AUTHOR]

The structural and optical properties of magnetron sputtered thin films of (ZnO)1−x(GaN)x deposited on zinc oxide, sapphire, and silicon oxide are studied as a function of strain accumulation and post‐deposition anneals at 600–800 °C. For the experimental conditions studied, we found that different amounts of tensile strain accumulated in the samples practically does not affect the strong bandbowing effect, that is, optical bandgap, observed in the as‐deposited alloys. In its turn, post‐deposition annealing results in a reduction of the tensile strain and dislocation density in the films, as measured by both X‐ray diffraction and transmission electron microscopy, corroborating an increase in the crystal quality. In addition, the grain size is found to increase with annealing temperature, for example, mean values of 20 nm up to 50 nm were measured for the alloys with x = 0.15. Meanwhile, the full‐width at half maximum of the (0002) X‐ray diffraction reflection increases with annealing temperature, but with only a small increase in bandgap energies for the x = 0.15 sample. However, this observation was explained combining the experimental data and first‐principles calculations based on density functional theory, showing that the increase in the amount of Ga‐N bonds lowers the total energy of the system. As such, we conclude that the thermal treatments increase the Ga‐N ordering, resulting in several contributions or a widening of the diffraction peaks. [ABSTRACT FROM AUTHOR]

This study investigated Lu doping of Ba0.5La0.5CoO3 and its influence on the exsolution of oxide nanoparticles (NPs). As a result of Lu doping, we observed the phase segregation into the main Ba0.4La0.6Co0.85Lu0.15O3 (BLCO–Lu) phase and the secondary Ba0.85La0.15Co0.75Lu0.25O3 (BCO–Lu) phase. We noticed the exsolution of BCO–Lu nanoparticles on the main BLCO–Lu phase. Moreover, the BLCO–Lu phase exsolved in the form of nanoparticles on the adjacent BCO–Lu grains. That shows that the phases are covered with mutually exsolved oxide NPs. In addition, trace amounts of the BaLuCo4O7 phase are detected. We noticed that the exsolved oxides even in the as-prepared sample were fine (average size of 18 nm), and well distributed with a dense population of NPs above 280 per 1 μm2. Furthermore, we showed that the size and shape of the exsolved oxide NPs can be controlled by varying the annealing temperature. For example, at 800 °C the exsolved oxides segregate and form two different shapes; spherical and cuboidal, with an average size of 31 nm and NP population of about 23 NPs per μm2. Meanwhile, with lowering the temperature to 400 °C the oxides form only spherical and quite evenly distributed NPs with the occurrence of 137 NPs per 1 μm2. The obtained results open the possibility of tailoring a novel, more catalytically active material for future applications in electrochemical devices. [ABSTRACT FROM AUTHOR]

Synthesis of Mo 2 C bare MXenes, without surface terminations groups, via chemical vapor deposition (CVD) on metal foils is scientifically a very intriguing crystal growth process, and there are still challenges and limited fundamental understanding to overcome to obtain high yield and wide crystal size lateral growth. Achieving large area coverage via direct growth is scientifically vital to utilize the full potential of their unique properties in different applications. In this study, we sought to expand the boundaries of the current CVD growth approach for Mo 2 C MXenes and gain insights into the possibilities and limitations of large area growth, with a particular focus on controlling Mo concentration. We report a facile modification of their typical CVD growth protocol and show its influence on the Mo 2 C synthesis, with growth times spanning up to 3 h. Specifically, prior to initiating the CVD growth process, we introduced a holding step in temperature at 1095 °C. This proved to be beneficial in increasing the Mo concentration on the liquid Cu growth surface. We achieved an average Mo 2 C crystals coverage of approximately 50% of the growth substrate area, increased tendency of coalescence and merging of individual flakes, and lateral flake sizes up to 170 μ m wide. To gain deeper understanding into their CVD growth behavior, we conducted a systematic investigation of the effect of several factors, including (i) a holding step time on Mo diffusion rate through molten Cu, (ii) the Cu foil thickness over the Mo foil, and (iii) the CVD growth time. Phase, chemical and microstructural characterization by x-ray diffraction, x-ray photon spectroscopy, SEM and scanning/transmission electron microscopy revealed that the grown crystals are single phase α -Mo 2 C. Furthermore, insights gained from this study sheds light on crucial factors and inherent limitations that are essential to consider and may help guide future research progress in CVD growth of bare MXenes., (Creative Commons Attribution license.)

Direct evidence of N 2 formation after annealing of (ZnO) 1-x (GaN) x alloys was revealed. N 2 was trapped by V Zn+Ga -clusters, forming faceted voids along grain boundaries. This study shows that N-N bonding is a competitive path for nitrogen after annealing, in addition to the increasing Ga-N bonds, indicating that N in O substitution sites (N O ) is not a stable configuration.

Functionalizing transparent conducting oxides (TCOs) is an intriguing approach to expand the tunability and operation of optoelectronic devices. For example, forming nanoparticles that act as quantum wells or barriers in zinc oxide (ZnO), one of the main TCOs today, may expand its optical and electronic tunability. In this work, 800 keV Ge ions have been implanted at a dose of 1 × 10 16 cm -2 into crystalline ZnO. After annealing at 1000 °C embedded disk-shaped particles with diameters up to 100 nm are formed. Scanning transmission electron microscopy shows that these are particles of the trigonal Zn 2 GeO 4 phase. The particles are terminated by atomically sharp facets of the type {11 [Formula: see text] 0}, and the interface between the matrix and particles is decorated with misfit dislocations in order to accommodate the lattice mismatch between the two crystals. Electron energy loss spectroscopy has been employed to measure the band gap of individual nanoparticles, showing an onset of band-to-band transitions at 5.03 ± 0.02 eV. This work illustrates the advantages of using STEM characterization methods, where information of structure, growth, and properties can be directly obtained.