Sol-Gel Synthesis of Solid Solution Based on Cerate-Zirconate Ceramics

Ceramics powders based on cerate-zirconate such as yttrium-doped barium cerate-zirconate, BaCe0.54Zr0.36Y0.1O3 (BCZY) have been used as electrolyte materials for proton-conducting fuel cell (PCFC) application. High purity of the ceramics powders are traditionally prepared by solid state reaction (SSR) method at a high processing temperature (> 1400 °C). Alternatively, sol-gel (SG) technique and high pressure – high temperature (HP-HT) batch wise reactor system using supercritical fluids (SCFs) method are introduced to synthesis the powders at a lower temperature. To achieve the goals in producing the ceramics powders with better properties than SSR method, few critical parameters for both SG and SG assisted SCFs methods are determined. This study reports the effects of different chemical agents (chelating agent and surfactant) in SG method and the effects of pressure and temperature of HP-HT batch wise reactor system using ethanol as solvent on the phase purity and microstructure of the BCZY powders. Chelating agent (triethylenetetramine, TETA) and surfactant (Brij-97) aided to produce a single perovskite phase of BCZY at calcination temperatures of 1100 °C and 950 °C, respectively. On the other hand, a single perovskite phase of BCZY was obtained via SCFs assisted with sol-gel (SG-SCFs) method. The optimum characteristics of BCZY powder was found in the one prepared at P = 2 MPa and T = 150 °C and 200 °C. Particles of the powders produced by SG and SG-SCFs methods are spherical in-shape. As proven, SG method is able to produce better phase purity and homogenize BCZY powder at lower processing temperature that meets criteria to be used as an electrolyte material.

A single-/double-perovskite composite with an overwhelming single-perovskite phase for the oxygen reduction reaction at intermediate temperatures

Enhanced oxygen reduction reaction over a single-/double-perovskite composite with a nominal formula of SrCo0.7Fe0.2W0.1O3−δ.

Effects of Sr Doping Content on the Structure and Morphologies of La0.7SrxCa0.3-xMnO3

The La0.7SrxCa0.3-xMnO3 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) were prepared by combining sol-gel method and high temperature sintering. The effects of Sr doping content on the structure and morphologies of the La0.7SrxCa0.3-xMnO3 finally sintered at 1050°C/1250°C were investigated based on the analyses of X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The results show that the La0.7SrxCa0.3-xMnO3 exhibit single perovskite phase and the change of Sr doping content can result in phase structure transition. The La0.7SrxCa0.3-xMnO3 samples are rhombohedra structure in the range of 0.15≤x≤0.3. When x is no more than 0.1, the La0.7SrxCa0.3-xMnO3 samples sintered at 1050°C present distorted cubic structure. The microstructure of La0.7SrxCa0.3-xMnO3 sintered at 1050°C for 5h becomes more and more looser and its grains tend to refinement with the increase of Sr doping content when x is no less than 0.05. Increasing the final sintering temperature can improve the density and promote the grain growth of La0.7SrxCa0.3-xMnO3. In order to gain a dense microstructure, the final sintering temperature of La0.7SrxCa0.3-xMnO3 should be higher than 1050°C and should be suitably increased with the increase of Sr doping content.

Dielectric Properties of Mn, Co, and Ni-Doped LaSrFeO3 Films with Different Annealing Atmosphere

Mn, Co, and Ni-doped La0.5Sr0.5FeO3 thin films were prepared by the sol-gel technique with different annesling atmosphere. The structure and dielectric properties of the films were researched by XRD, SEM and Agilent. The study found that LSF-Mn (Co, Ni) films under the argon annealing atmosphere were have optimal dielectric properties. And Mn, Co, Ni elements are integrated into La0.5Sr0.5FeO3 lattices with the single perovskite phase. And uniform grain was distribution on the film surface.

Evolution of Phase Structure and Micro-Morphologies of the La0.7M0.3MnO3 (M=Ca, Sr) Sintered at Different Temperature

The La0.7M0.3MnO3 (M=Ca, Sr) were synthesized by combining sol-gel technique and solid state sintering method. The evolutions of phase structure and micro-morphologies of the La0.7M0.3MnO3 with final sintering temperature (950-1250°C) were investigated. The results show that the La0.7Ca0.3MnO3 compounds exhibit single perovskite phase with cubic structure and the La0.7Sr0.3MnO3 compounds exhibit single perovskite phase with rhombohedra structure. The final sintering temperature has no obvious effect on the phase structure of La0.7Ca0.3MnO3. However, the density and grain size of La0.7M0.3MnO3 (M=Ca, Sr) increase with the increase of the final sintering temperature. Moreover, the micro-morphologies of La0.7Ca0.3MnO3 are more sensitive to final sintering temperature compared with that of La0.7Sr0.3MnO3. When sintering temperature is no less than 1150°C, the La0.7Ca0.3MnO3 has hardly any pore. After sintering at no less than 1250°C, the La0.7Sr0.3MnO3 becomes dense.

Structural and High Frequency Dielectric Properties of Ba(ZrxTi1-x)O3 Films Prepared by Reactive Magnetron Sputtering Using Metal Targets

Ba (ZrxTi1-x)O3(BZT) films with different Zr contents were deposited on (100)MgO substrates by RF-magnetron reactive sputtering using metal targets. The BZT films epitaxially grew on MgO substrates with only (001)/(100) orientation and had a single perovskite phase. In all cases, the ratio of Ba/Ti was stoichiometry and BZT films possess a dense microstructure. The effect of Zr content on the crystal structure was studied. The grain size was decreased with increasing Zr content. The dielectric properties of the BZT films were also measured at high frequencies region. The reliability of the high-frequency dielectric properties extracted from the measuredS11reflection coefficients. The capacitance for BZT film showed little dispersion and low dielectric loss at 1-18 GHz. These results indicated that we succeeded in depositing high-quality and potential tunable ferroelectrics for high frequency applications.

Structure and Dielectric Properties of Mg, Cr-Doped LaSrFeO3 Films

Mg-doped LaFeO3 thin film and Mg, Cr-doped La0.5Sr0.5FeO3 thin films were prepared by the sol-gel method. The change rules of structure and dielectric properties of the films were studied by XRD, SEM, and Agilent. The dielectric properties of La0.5Sr0.5FeO3 and LaFeO3 films were improved by the substitute with Mg and Cr. The doping amount of Mg and Cr for the optimal dielectric properties of La0.5Sr0.5FeO3 films is 45mol%, 25mol%, respectively, and for LaFeO3, the doping amount of Mg is 8mol%. The observed pure perovskite phase of the doped films suggested the dissolution of Mn, Co, and Ni in La0.5Sr0.5FeO3 crystal lattice. Mg and Cr were integrate in the lattice of LaFeO3 and La0.5Sr0.5FeO3, and mineral is single perovskite phase. The surface of the film is smooth, without cracks, surface grain size distribution and had uniform grain size.

Preparation of Bismuth Copper Based Perovskite-Type Ceramics and their Piezoelectric Properties

The structural, and dielectric and piezoelectric properties of 0.3BaTiO3- 0.1x(x= Bi (Mg1/2Ti1/2)O3, Bi (Cu1/2Ti1/2)O3, Bi (Cu2/3Nb1/3)O3, (Bi1/2K1/2)(Cu1/3Nb2/3)O3) 0.6BiFeO3ceramics were studied. The relative density of all the samples was more than 94 %. A single perovskite phase was obtained for the samples, and the crystal structure was pseudo-cubic. The Curie temperature ofx=Bi (Mg1/2Ti1/2)O3and Bi (Cu1/2Ti1/2)O3system ceramics was higher than 400 °C. The apparent piezoelectric constantd33* ofx=Bi (Mg1/2Ti1/2)O3, Bi (Cu1/2Ti1/2)O3, Bi (Cu2/3Nb1/3)O3and (Bi1/2K1/2)(Cu1/3Nb2/3)O3system ceramics was 311, 212, 75 and 70 pm/V, respectively.

Microstructure and Piezoelectric Properties of BaTiO3-Bi(Mg1/2Ti1/2)O3-BiFeO3 Ceramics

Barium titanate (BaTiO3, BT)-bismuth magnesium titanate (Bi (Mg1/2Ti1/2)O3, BMT)-bismuth ferrite (BiFeO3, BF) solid solution ceramics were prepared using a conventional solidstate synthesis, and their piezoelectric properties and microstructure were investigated. Strain electric field curves of the 0.3BT-0.1BMT-0.6BF ceramics with a single perovskite phase were ferroelectric butterfly-like curves. A strain maximum / electric field maximum (Smax/Emax) was 330 pm/V. Transmission electron microscopy revealed ferroelectric-like domain structure in the 0.3BT-0.1BMT-0.6BF ceramics.

Permittivity and modulus spectroscopic study of BaFe0.5Nb0.5O3 ceramics

Ba(Fe0.5Nb0.5)O3 (BFN) powder was synthesized in single perovskite phase by conventional solid state reaction route and BFN ceramic was obtained by uniaxial pressing and sintering at 1350?C. Complex immittance like: permittivity and modulus spectroscopic formalism were simultaneously used to explain dielectric behaviour of the ceramics. The activation energy calculated from dielectric relaxation below 100?C was found to be ~ 0.19 eV. The activation energy obtained from modulus spectra above 100?C was ~0.59 eV. The space charge polarization model was used to explain the origin of relaxation and ?giant? permittivity of BFN ceramics near room temperature.