Papers by Keyword: Perovskite

Abstract: The sintering behaviors and microwave dielectric properties of the Ca_0.6La_0.8/3TiO₃-Li_0.5Nd_0.5TiO₃ (abbreviated CLLNT) ceramics doped by small amounts of ZnO-B₂O₃-SiO₂ glass were investigated in this paper. The adding of ZnO-B₂O₃-SiO₂ glass improved the densifications of the CLLNT ceramics and the sintering temperature of the CLLNT ceramic had been efficiently lowered to 1050°C. Especially, the 8wt% ZnO-B₂O₃-SiO₂ glass doped CLLNT ceramic sintered at 1050°C for 3 h has optimum microwave dielectric properties of Kr=89, Q×f=1445GHz, and TCF=11.4 ppm/°C and it should be a suitable candidate for LTCC applications.

Abstract: Lead free Na_0.5Bi_0.5TiO₃ (NBT) and (Na_0.5Bi_0.5TiO₃)1-x(CaTiO₃)x (NBT-CT) piezoelectric ceramics with the perovskite structure were studied. The NBT and NBT-CT samples were synthesized using a solid-state reaction method and characterized with X-ray diffraction (XRD), Raman spectroscopy and dielectric measurements for several compositions (x = 0, 0.07, 0.15) at room temperature. The XRD analysis showed a stabilization of a rhombohedral phase at a low concentration of Ca (0 < x <0.15), whereas Raman spectra reveal a strong modification for the sample with x = 0.15. The dielectric properties of these ceramics were studied by measuring impedance in the 79-451K temperature range for unpoled and field cooling with an electric field (FC) conditions.

Abstract: An organic–inorganic hybrid perovskite (C₆H₅CH₂NH₃)₂CuCl₄was synthesized successfully by solution method at room temperature and the thin film of (C₆H₅CH₂NH₃)₂CuCl₄ was also prepared by spin-coating on the quartz substrate. The perovskite and the film were characterized with X-ray diffraction (XRD), Scan electronic microscope (SEM), Atomic force microscope (AFM), Fourier transform infrared spectroscopy and Thermo Gravimetric Analyzer. Results show that the obtained perovskite has unique layer structure and good thermal stability with melting point around 243.3°C. And the prepared film appears very smooth, continuous and uniform with a grain size of 0.1μm, highly oriented with the (0 0 l) planes perpendicular to the substrate surface. Its optical photoluminescence spectrum mainly depends on the inorganic part so the bandgap can be tuned by changing the inorganic composition. The carrier mobility is around 0.26cm²V^-1S^-1 , which indicates its potential application in field effect transistor with improved film quality.

Abstract: La_1-xSr_xMnO_3+σ perovskite/ySBA-15(x=0, 0.1, 0.2, 0.3、y=0, 1, 2, 3) catalyzers were prepared by two different methods, which are the hard-templating and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray fluorescence spectroscopy(XRD) and N₂ adsorption/desorption(BET). Their catalytic activity in the oxidation of CO was evaluated. BET and SEM results showed that the repeated template samples had higher surface area(143.7m2/g) and smaller particle size(18nm). The catalytic activity for CO reached the highest value when x=0.2 and y=2. The repeated template samples had higher activity than the sol-gel samples due to the higher surface area.

Abstract: This study aims to synthesize Cr doped Perovskite brown pigments. The pigment were synthesized by doping Cr₂O₃(0.01 ~ 0.05mole) for TiO₂(0.993 ~ 0.963 mole) at 1150 ~ 1350°C. The samples were characterized by X-ray diffraction (XRD), Raman Spectrometer, Scanning Electron Microscope(SEM) and the UV/Vis spectroscopy. The optimum composition was CaCr_0.03Ti_0.978O₃ and heating condition was 1300°C for 3h of soaking time. The doped Cr ion for Perovskite was observed to be Cr(Ⅲ) and Cr(Ⅳ). The brown color was mixed with violet doped by Cr⁴⁺(³A₂ → ³T₂) and Blueish-Green doped by Cr³⁺(4A_2g → ⁴F_1g). The results of SEM analysis showed the Perovskite structure and the particle size was approximately 2µm. The color in Frit 6060 glaze adding 10wt% pigment was Redish Brown, and CIE Lab parameters were L^*= 41.53, a^*=13.27 and b^*=9.94 .

Abstract: In order to study the morphology and catalytic oxidation performance of LaMnO3 nanoparticles after A or B site doping , the sol-gel methods is applied, the La1-xSrxMnO3 and LaCuxMn1-xO3（x=0.1, 0.2, 0.3, 0.4, 0.5) nanoparticles are prepared. The diameter of particles and morphology-distribution of naniparticles with different doping amounts are analyzed by X-ray diffraction (XRD), scan electric microscope (SEM) and related software. With the framework of the experiment, the average diameter of particles is between 16-21nm with better chemical homogeneity and have higher surface area. At the same time, the catalytic oxidation of nanoparticle under different doping amounts is also studied. Tests results show that nanoparticle has excellent catalytic oxidation performance, and with the increase of doping amount, the catalytic activity of the particle increase first and decrease afterwards with the increase of A or B site doping amount, the best performance presents at X=0.2 of A or B doping concentration. The effect of lattice deformation arising from the dopants, which leads to the decrease of the catalytic performance, can not be ignored at higher doping concentration anymore. Under the same doping amounts, the catalytic performance of B-site doped is better than A-site.

Abstract: An estimation method of the influence of interfaces on properties in perovskite-type oxide thin-film capacitors is presented. We proposed a modified Schottky model that can be employed to explain the electric properties of metal/perovskite-type oxide junctions. The modified model considers the electric field dependence of permittivity and the flow of electrons from metal to defect states located in the band gap of the perovskite oxide. The simulation based on this model could successfully describe the results of capacitance-voltage measurements of junctions between metals (Pt, Au, and Ag) and Nb-doped SrTiO₃, which were not explained by the conventional Schottky model. Additionally, a simulation for a thin-film capacitor with hysteretic behavior could depict an asymmetric capacitance-voltage curve.

Abstract: To determine the effect of the annealing atmosphere on oxygen diffusion through Ba_0.95La_0.05FeO_3-d pellets, ¹⁸O₂ tracer diffusion and high-resolution secondary ion mapping were performed. When annealing in air, the ¹⁸O concentration around the surface up to a depth of 40 µm was almost constant. On the other hand, when annealing in vacuum, the ¹⁸O concentration obviously decreased. High-resolution secondary ion mapping indicated that the ¹⁸O concentration around the grain boundary was reduced. These results suggested that the grain boundary of BLF annealed in vacuum prevents oxygen diffusion.

Abstract: The synthesis of Ba_1-xSr_xTiO₃ (BST) powders was attempted using KOH-KNO3 molten salt. The starting materials, Ba(NO3)2, Sr(NO3)2 ,TiO2,and the mixed salt of KOH-KNO3, were well-mixed. The mixture was heated at 300 to 500°C for 1 hour, and the product was thoroughly washed with de- ionized hot water. When the mixture containing excess TiO2 was used, single-phase BST powders with a particle size of 10~50nm were obtained.

Abstract: Structural changes induced by oxygen vacancies in tetragonal phase BaTiO₃ are studied with first principles calculations within density functional theory. In our calculations, the incorporation of oxygen vacancies greatly decreases c/a ratio of the tetragonal phase BaTiO₃, and a phase transition from tetragonal to cubic phase occurs when the incorporation of the oxygen vacancies reaches about 4%. Our results also shows that the generation of the oxygen vacancies slightly increases the volume of BaTiO₃, and the increases are typically less than 0.5% even in heavily reduced conditions.