Study on thermolysis process of a new hydrated and protonated perovskite-like oxides H2K0.5Bi2.5Ti4O13·yH2O (original) (raw)
Related papers
Processing and characterization of CaTiO3 perovskite ceramics
Processing and Application of Ceramics, 2014
Calcium titanate (CaTiO 3 ) ceramics with perovskite structure were produced by solid state reaction. Calcium carbonate (CaCO 3 ) and titanium dioxide (TiO 2 ) were mixed (in molar ratios 1/1 and 3/2), and the obtained mixtures were calcined at 1150°C in successive thermal cycles. The obtained samples were characterized by differential thermal analysis, thermogravimetry, X-ray diffraction, measurement of particle size distribution and linear thermal shrinkage. XRD results indicated that the samples have perovskite CaTiO 3 structure with small amount of secondary CaO and TiO 2 phases, and their phase composition depends on the heat treatment conditions. The measured values of electrical resistivity were within the characteristic range of insulating materials and approach values corresponding to semiconducting ceramics.
New data on protonation and hydration of perovskite-type layered oxide KCa2Nb3O10
Journal of Thermal Analysis and Calorimetry, 2020
Protonation and hydration processes of layered perovskite-like oxide KCa 2 Nb 3 O 10 during the reaction with nitric acid solutions with different concentrations were studied by means of TG, STA + MS, XRD, SEM, EDX and ICP methods. It was found that despite the absence of significant changes in crystal structure, treatment of KCa 2 Nb 3 O 10 with water leads to the partial substitution of K + with H + (about 15% exchange), while a number of new hydrated protonated phases H x K 1−x Ca 2 Nb 3 O 10 •yH 2 O with higher exchange (50-90%) may be obtained using moderate acid concentrations (0.1-3 M HNO 3) varying reaction time. It was shown that production of the fully protonated form requires the minimum 3 M concentration of the acid and 24 h reaction time.
Journal of the European Ceramic Society, 2011
High-temperature proton conducting perovskite oxides have been fabricated by directional solidification using a laser-heated floating zone (LHFZ) method. Several families of compositions were selected: SrCe 1−x Y x O 3−δ (with x = 0.1, 0.2), BaCe 1−x M x O 3−δ (with M = Y, Yb and Ca; x = 0.05, 0.2), Sr 3 Ca 1.18 Nb 1.82 O 9−δ , SrZr 0.8 Y 0.2 O 3−δ and SrTi 0.95 Sc 0.05 O 3−δ. The resulting microstructures were characterized by electron microscopy and X-ray diffraction. The compounds exhibit a singular microstructure consisting of strongly textured crystalline cells surrounded by an intercellular amorphous phase. Compressive mechanical tests were performed at elevated temperatures in air at constant strain rate to evaluate the creep resistance. The results are discussed in terms of ionic radius, degree of aliovalence and content of dopant cations.
New Na 0.5 Bi 0.5 TiO 3 –NaTaO 3 -Based Perovskite Ceramics
Journal of the American Ceramic Society, 2007
X-ray diffraction analyses and scanning electron microscopy revealed that Na 0.5 Bi 0.5 TiO 3 (NBT) and NaTaO 3 (NTa) form solid solutions across the whole concentration range. With increasing NTa content the symmetry of the solid solutions gradually changed from rhombohedral, on the NBT-rich side, to orthorhombic, on the NTa-rich side. No morphotropic phase boundary was found between these phases. With increasing NTa content, the perovskite lattice parameter (a p) and the sintering temperature increase, whereas the grain size decreases. In the case of pure NTa, ceramics with a secondary phase were obtained, identified as Na 2 Ta 8 O 21 , which was formed during the sintering process. A study of the dielectric properties showed that with an increasing concentration of NTa, there was a reduction and broadening of the permittivity maximum, a reduction of the temperatures of the dielectric anomalies, and a reduction of the dielectric losses.
Low-temperature aqueous synthesis (LTAS) of ceramic powders with perovskite structure
Journal of Materials Science Letters, 1996
Barium metatitanate is among the most extensively employed ceramics for electronic applications, mainly in the form of miniaturized multilayer and grain boundary layer capacitors with large capacitance values for energy storage. It can also be employed in the field of acoustic transducers, where it can be competitive with PZT when a good hydrostatic response is required. A very fine grained microstructure is often required for many practical purposes, which is, however, difficult to achieve through traditional preparation methods [1]. Considerable effort has been devoted to discovering alternative syntheses to obtain fine powders, especially via metallo-organic precursors . Recently, submicron BaTiO3 crystalline powder has been prepared in our laboratory using a low-temperature aqueous synthesis (LTAS) . Due to the very fine particle size (diameter <0.03#m), relative lowtemperature sintering is possible which reduces grain growth. High purity and reproducibility are achieved through this procedure; excellent control of the Ba:Ti ratio is also obtained, which is of great technological interest as dielectric ageing as well as other dielectric properties strongly depend on it. LTAS can also be used to produce ferroelectric materials with controlled composition, introducing suitable homogeneously dispersed additives and dopants which modify the dielectric characteristics according to the user's requirements .
High Entropy Oxide Phases with Perovskite Structure
Nanomaterials
The possibility of the formation of high entropy single-phase perovskites using solid-state sintering was investigated. The BaO–SrO–CaO–MgO–PbO–TiO2, BaO–SrO–CaO–MgO–PbO–Fe2O3 and Na2O–K2O–CaO–La2O3–Ce2O3–TiO2 oxide systems were investigated. The optimal synthesis temperature is found between 1150 and 1400 °C, at which the microcrystalline single phase with perovskite structure was produced. The morphology, chemical composition, crystal parameters and dielectric properties were studied and compared with that of pure BaTiO3. According to the EDX data, the single-phase product has a formula of Na0.30K0.07Ca0.24La0.18Ce0.21TiO3 and a cubic structure.
Hydrothermal synthesis of perovskite and pyrochlore powders of potassium tantalate
Journal of Materials Research, 2002
Potassium tantalate powders were hydrothermally synthesized at 100 to 200 °C in 4 to 15 M aqueous KOH solutions. A defect pyrochlore, Kta2O5(OH). nH2O (n ≈ 1.4), was obtained at 4 M KOH, but at 7–12 M KOH, this pyrochlore was gradually replaced by a defect perovskite as the stable phase. At 15 M KOH, there was no intermediate pyrochlore, only a defect perovskite, 0.85Ta0.92O2.43(OH)0.57 0.15H2O. Synthesis at higher KOH concentrations led to greater incorporation of protons in the perovskite structures. The potassium vacancies required for charge compensation of incorporated protons could accommodate water molecules in the perovskite structure.