Effects of flux treatment on morphology of single-crystalline BaNbO 2 N particles (original) (raw)
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Facile in-situ synthesis of NbB 2 nanoparticles at low temperature
Niobium diboride (NbB 2) nanoparticles have been successfully synthesized at 800 C in a single step from niobium penta-oxide (Nb 2 O 5), magnesium (Mg) and borax (Na 2 B 4 O 7 $10H 2 O) in an autoclave. The synthesis temperature and holding time have been optimized to obtain single phase NbB 2. The phase determination, thermal stability and morphological features of synthesized samples have been analyzed by X-ray diffraction (XRD), thermal gravimetric-differential scanning calorimetry (TG-DSC) and electron microscopic technique respectively. Williamson-Hall (W-H) analysis has also been done to observe the effects of synthesis parameters (temperature and holding time) on crystal distortion. With the help of XRD, microstructural features and thermodynamic calculations, formation mechanism for the synthesized samples has been predicted.
Structure of NaNbO3: xMn Single Crystals at Room Temperature
Crystal Research and Technology, 2001
A series of NaNbO 3 : x Mn single crystals had been obtained by flux method. Manganese oxide was introduced to obtain nominal Mn content within 10%mol. Real concentration of Mn dopant was determined as one order lower. It was concluded from valence band analysis that Mn ions built in niobium sublatice mainly. All the samples exhibited discontinuous structural antiferroelectric phase transition proved by DTA test. The phase transition temperature lowers, while the real concentration of Mn increases, with the rate -15 K/%wt (Mn). The X-ray experimental spectrum remains in agreement with the spectrum generated for perovskite NaNbO3 when orthorhombic Pbcm space group was chosen for simulation. The evolution of lattice constant with Mn concentration was examined
A co-precipitation technique to prepare BiNbO4 powders
A simple co-precipitation technique was successfully used for the preparation of pure ultrafine single phase BiNbO 4 . A standard ammonium hydroxide solution was used to precipitate Bi 3+ and Ta 5+ cations as hydroxides simultaneously under basic conditions. For comparison, BN powders were also prepared by the traditional solid-state method. It is observed that the co-precipitation technique produces BiNbO 4 on heating at 600 8C, whereas complete phase formation occurs only at 800 8C in the solid-state method. The phase contents and lattice parameters were studied by powder X-ray diffraction (XRD). #
Morphology control of SrBi2Nb2O9 prepared by a modified chemical method
Science of Sintering, 2019
SrBi 2 NbO 9 compounds were prepared through three methods: oxalate coprecipitation, molten salt synthesis and polymerizable complex. The effect of the molecular precursor route has also been investigated. For oxalate co-precipitation method, a solution obtained from acid oxalate, niobium oxide, bismuth nitrate and strontium nitrate are precipitated by ammoniac solution. Then, the precipitated sample is calcined at 1100 °C. A methanol-citric acid solution of solution of NbCl 5 , ethylene glycol, bismuth and strontium nitrates were used as precursors. A black powder ash was crystallized by heat-treating at 1100 °C. Molten salt technique using oxides and carbonate as starting materials and NaCl and KCl to form a reaction medium. The formation temperature was at 1110 °C. Multiple characterizations mainly X-ray diffraction, Fourier transformed infrared spectroscopy and scanning electron microscopy (SEM) measurements have provided to validate the structural feature. Careful, X-ray diffraction analysis showed the presence of two-layered Aurivillius structure. The crystallite size is discussed by Scherrer and Williamson-Hall approaches. SEM images of SrBi 2 NbO 9 ceramics showed plate-like, polygonal and structureless morphologies obtained at different synthesis conditions. Whatever the synthesis process, there is no change on the band of infrared spectra.
Bulletin of Materials Science
Sr x Ba 1-x Nb 2 O 6 (with x = 0⋅ ⋅4, 0⋅ ⋅5 and 0⋅ ⋅6) powders have been prepared by thermolysis of aqueous precursor solutions consisting of triethanolamine (TEA), niobium tartarate and, EDTA complexes of strontium and barium ions. Complete evaporation of the precursor solution by heating at ~ 200°C, yields in a fluffy, mesoporous carbon rich precursor material, which on calcination at 750°C/2 h has resulted in the pure SBN powders. The crystallite and average particle sizes are found to be around 15 nm and 20 nm, respectively. Keywords. Low temperature preparation; nanocrystalline solid solution; Sr x Ba 1-x Nb 2 O 6 .
Kinetics of Nb incorporation into barium titanate
Journal of Physics and Chemistry of Solids, 2001
The diffusion coef®cient of Nb in BaTiO 3 single crystal was determined from the Nb diffusion pro®le in the temperature range 1530±1723 K in air. The Arrhenius plot of the obtained diffusion data indicates that there is a change in the diffusion mechanism at 1626 K. At 1530 K these data are consistent with the chemical diffusion coef®cient of Nb-doped BaTiO 3 . It was found that the transport in Nb at 1530 K and above this temperature occurs according to a different mechanism. Below 1481 K the process of Nb incorporation into BaTiO 3 is substantially retarded. q
Preparation of single crystalline Sr 0.5Ba 0.5Nb 2O 6 particles
Journal of The European Ceramic Society, 2006
Single crystalline and agglomerate-free ceramic particles are important for fabrication of grain-oriented ceramics by the self-assemble processes. In the present work, preparation of single crystalline Sr 0.5 Ba 0.5 Nb 2 O 6 particles was first explored by traditional solid-state reaction and molten-salt synthesis methods. The results show that the particles synthesized by solid-state reaction were spherical, hard-aggregated and polycrystalline. Molten salt synthesis provides sub-micrometer anisotropic single crystalline Sr 0.5 Ba 0.5 Nb 2 O 6 particles and the morphology of a particle may be adjusted by changing synthesis conditions. The synthesized particles have uniform size distribution and are easily dispersed, thus may suit self-assemble processes to prepare grain-oriented ceramics. Furthermore, effects of synthesis conditions in molten salt synthesis, on the phase formation, morphology and size distribution of SBN particles were investigated.