The evolution of vacancy-type crystalline defects across the transition from anatase to rutile structure titanium dioxide (TiO2) nanoparticles during high-temperature annealing in oxygen and argon is studied by using positron lifetime coincidence Doppler broadening spectroscopic measurements. TiO2 were synthesized through a simple sol–gel chemical route. changes phase lattice parameters upon thermal treatment investigated X-ray diffraction high-resolution transmission electron microscopy,...

Nanocrystalline $\mathrm{Ni}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ particles were synthesized in a $\mathrm{Si}{\mathrm{O}}_{2}$ matrix and characterized by x-ray diffraction TEM observations. Positron lifetimes these samples measured. The measured positron indicated admixtures of contributions from annihilations within the nanoparticles, at nanoparticle-$\mathrm{Si}{\mathrm{O}}_{2}$ interfaces, matrix. individual calculated based on known characteristics electron-positron annihilation solids...

By carrying out positron lifetime measurements in zinc ferrite (ZnFe2O4) samples of various grain sizes down to 5 nm, the defect microstructures have been identified. In bulk composed grains large sizes, positrons were trapped by monovacancies crystalline structure. Upon reduction nanometer dimensions, get selectively at either diffused vacancies on surfaces and intergranular regions. Below about 9 undergo transformation from normal spinel structure inverse phase. A concomitant lattice...

Extension of photoactivity TiO2 to the visible region is achievable via effective control over intrinsic defects such as oxygen and Ti vacancies, which has several applications in photocatalysis sensing. We present here first observation an apparent bandgap narrowing tuning effect due vacancy cluster transformation rutile structures 1.84 eV from bulk 3 eV. A gradual divacancies (V Ti–O) tri vacancies () achieved through a controlled solvothermal scheme appears result tunability, supported by...

Meticulous surface engineering of layered structures toward new functionalities is a demanding challenge to the scientific community. Here, we introduce defects on varied MoS2 surfaces by suitable doping nitrogen atoms in sulfur-rich reaction environment, resulting stable and scalable phase conversion. The experimental characterizations along with theoretical calculations within framework density functional theory establish impact stabilization reconstruction 2H 1T phase. as-synthesized...

Positron lifetime and Doppler broadening measurements on nanocrystalline niobium over a wide range of grain sizes (5--35 nm) were performed. Significant changes in the structure properties boundaries intercrystalline regions observed when size was reduced below 10 nm. While positron at sharply increased owing to an increase excess free volume associated with atoms, atomic reordering brought remarkable redistribution electron momenta boundaries. A model-based calculation atoms supported these...

Doping in ceria (CeO2) nanoparticles with europium (Eu) of varying concentrations (0, 0.1, 0.5, …, 50 atom%) is studied using complementary experimental techniques and novel observations were made during the investigation. The immediate observable effect was a distinct reduction particle sizes increasing Eu concentration attributed to relaxation strain introduced due replacement Ce(4+) ions by Eu(3+) larger radius. However, this general trend reversed doping range 0.1-1 atom% Ce(3+)...

A systematic study on the room temperature ferromagnetism (RTFM) in undoped and Mn-doped ZnO nanoparticles (NPs) prepared by coprecipitation method has been reported. The neutral singly ionized zinc vacancy defects exhibited results of photoluminescence (PL), micro-Raman spectroscopy, electron paramagnetic resonance (EPR) studies are found to be ferromagnetic origin bare ZnO, it confirmed that Mn2+ ions substitutionally enter at Zn2+ sites wurtzite ZnO. positron annihilation coincidence...

X-ray diffraction and positron annihilation measurements were performed on the ball-milled nanocrystalline Fe powder over a wide range of crystallite sizes (9–90 nm). With increasing milling time, size reduction was accompanied by monotonic increase lattice parameter (i.e. expansion). The lifetime increased significantly due to enhanced from defects (excess vacancies, vacancy-clusters, etc.) generated at grain boundaries intercrystalline regions with progressive up 24 h (crystallite ∼ 12...

Cadmium oxide (CdO) micro-octahedrons and nanowires were synthesized by a simple solvothermal process using ethanol as solvent. The amount of NaOH the synthesis temperature key parameters to control phase morphology as-synthesized products. purity samples was determined through X-ray diffraction (XRD). Lower concentration higher-synthesis favored formation CdO micro/nanostructures. Morphologies products identified scanning electron microscopy (SEM) transmission (TEM). At higher low...

Multiferroics that permit manipulation of magnetization vector exclusively by electric fields have spawned extensive interest for memory and logic device applications.

Abstract Polymer membrane based gas transport and pervaporation processes are fast growing areas in separation technology have received wide attention as of ‘clean technology’. Mechanically stable novel polyhedral oligomeric silsesquioxane (POSS) embedded poly(vinyl alcohol) (PVA)/poly(ethylene oxide) (PEO) blend membranes were prepared by solution blending followed casting. The addition carboxymethyl cellulose enhanced the interfacial activities PVA PEO blends. peripheral organic...

Bipyramidal-shaped single crystalline nanocones of ZnO, doped with Mn2+ ions up to different concentrations, were synthesized through a solvothermal route and characterized by X-ray diffraction transmission electron microscopy. The compositional analysis was also carried out energy-dispersive X-rays (EDAX). Positron annihilation studies extract information on the vacancy-type defect clusters their evolution under doping, which may have major influence physical properties material. In undoped...

Ultrafine nickel oxide nanoparticles were prepared by sol–gel method using a solution of nitrate hexahydrate and ammonium hydroxide subsequently annealed in air at different temperatures the range 200–275 °C for hours to vary particle sizes. They characterised phase, purity, structure sizes X-ray diffraction high-resolution transmission electron microscopy. found polycrystalline nature possessed face-centred cubic (NaCl-type) with lattice parameter varying annealing temperature. The...

Positron annihilation spectroscopy (PAS) comprising of the measurements positron lifetime and coincidence Doppler broadening spectra has been carried out to understand monitor evolution vacancy-type defects arising from ionic deficiencies at lattice points multiferroic perovskite bismuth ferrite (BiFeO3) doped with 1, 5 10 at% gadolinium (Gd3+) ions. Negatively charged in form Bi3+ monovacancies were present undoped nanocrystallites, which strongly trapped positrons. During successive doping...

In an earlier work, the substitution of Zn²⁺ ions at tetrahedral sites nanocrystalline zinc ferrite (ZnFe₂O₄) by Ni²⁺ had been observed to cause a transformation from normal spinel structure inverse one.

Calcium-ion substitution to different concentrations in the normally insulating but wide band gap semiconductor magnesium oxide nanocrystallites was successfully achieved through a sol-gel route and synthesized samples were characterized by X-ray diffraction transmission electron microscopy. The of Mg2+ Ca2+ gave rise distinct variation nanocrystallite sizes lattice constants. energies (Eg = 5.04 5.50 eV) obtained from ultra-violet visible absorption spectroscopy hinted formation Positronium...