Query: Lanthanum Silicate

title: Effect of Boron Substitution on Oxide Ion Conduction in c Axis Oriented Apatite Type Lanthanum Silicate
abstract: Apatite type lanthanum silicate (LSO) is a material with high oxide ion conductivity in the low and intermediate temperature range (573 873 K) and is, therefore, a promising solid electrolyte for low temperature applications such as solid oxide fuel cells and oxygen sensors. Herein, the effect of B substitution at the Si site in a c axis oriented apatite type lanthanum silicate (La9.7Si5.3B0.7O26.2, c LSBO) polycrystal on oxide ion conduction is investigated. A highly c axis oriented LSBO polycrystal is fabricated by a vapor solid reaction in which a dense La2SiO5 disk is heated in B2O3 vapor at =1673 K. The oxide ion conductivity of c LSBO reaches 16 mS cm 1 at 678 K with an activation energy of 0.4 eV. The obtained oxide ion conductivity of c LSBO is approximately 190 times higher than that of yttria stabilized zirconia and 5.8 times higher than that of the polycrystalline c axis oriented nondoped lanthanum silicate. Based on 11B nuclear magnetic resonance measurements, B is located at the SiO4 site as.

title: Morphology and oxide ion conductivity of flux grown single crystals of BaO doped lanthanum silicate oxyapatite
abstract: Well faceted and chemically homogeneous single crystals of BaO doped lanthanum silicate oxyapatite were grown by a BaCl2 flux method. They were characterized by optical microscopy, scanning electron microscopy, electron probe microanalysis (EPMA) X ray diffractometry (XRD) and electrochemical impedance spectroscopy. The developed faces were identified for the two types of single crystals with different habit. The face indices were {100} {101} {110} and {210} for the prismatic crystals, and {100} {101} {111} and {001} for the isometric ones. With prismatic crystals, the general formula was derived from the numbers of cations determined by EPMA and structural data refined by XRD to be (La10 xBax)S=10(Si5.5+0.25x#0.5 0.25x)S=6O26 (1.78 x 1.81) where denotes a vacancy in Si site. We determined the oxide ion conductivity (s) of the prismatic single crystal of (La8.22Ba1.78)(Si5.94#0.06)O26 (x 1.78) along the elongation direction, which is parallel to the c axis. The s value steadily increased from 7.69 x 10 3 to 5.30 x 10 2 S cm 1 with increasing temperature from 823 to 1073 K. When compared at the same temperature, the s values were >230 times higher than those of the randomly grain oriented polycrystal with the same chemical composition, the latter of which ranged from 1.74 x 10 5 S cm 1 at 823 K to 2.24 x 10 4 S cm 1 at 1073 K. The remarkable difference in conductivity between the single crystal and randomly grain oriented polycrystal was found to be principally induced by the marked conduction anisotropy in the crystal structure.

title: Improving conductivity of apatite type lanthanum silicate by Nd and Zn co doping
abstract: The electrical properties of apatite type lanthanum silicate co doped with Nd and Zn has been investigated. The Nd and Zn co doped lanthanum silicate, La9.33NdxSi6 yZnyO26+(3x/2) y (0 x 1, y 0,1) are successfully synthesized by the urea nitrate combustion method. The phase, morphology and electrical properties are characterized by X ray diffraction, scanning electron microscopy and electrochemical impedance spectra, respectively. La9.33NdxSi6 yZnyO26+(3x/2) y ceramics has good apatite structure and high purity. The conductivity of La9.33NdxSi5ZnO25+(3x/2) first increases and then decreased accompanying with Nd content increasing, which higher than that of undoped La9.33Si6O26. The increase of the conductivity, which is attributed to Zn doped introduces oxygen vacancies and expands oxygen ions migration channel as well as Nd doped decreases the defect centers and increases the amount of interstitial oxygen ions. The decrease in conductivity is due to excess Nd blocking the oxygen ions migration channel. La9.33Nd0.8Si5ZnO26.2 exhibited the highest conductivity which values equal to 8.11 x 10 4 S cm 1 at 650 degC.

title: Synthesis and characterization of Ba2+ and W6+ co doped apatite type lanthanum silicate electrolytes
abstract: Abstract Ba2+ and W6+ co doped apatite type lanthanum silicate solid electrolytes La9.4Ba0.6Si6 xWxO27 d (x 0, 0.05, 0.1, 0.15, 0.2) were successfully synthesized by high temperature solid state method. The crystal structure, phase composition, microstructure, and electrical performance of samples were characterized by X ray diffraction, Raman spectroscopy, scanning electron microscopy, and electrochemical impedance spectroscopy, respectively. The dense co doped solid electrolyte materials sintered at 1550 degC for 5.5 h have good crystallinity and apatite type crystal structure. The influences of the co doped W6+ content on the properties of La9.4Ba0.6Si6 xWxO27 d were investigated. The grain structure gradually changes from equiaxed and columnar grains to equiaxed grains. After Ba2+ and W6+ are co doped, the lattice constant and cell volume are larger than those of La10Si6O27. The conductivities of the apatite lanthanum silicates are improved. La9.4Ba0.6Si5.9W0.1O26.8 exhibits the highest conductivity of 8.11 x 10 3 S cm 1 at 800 degC, whereas the conductivity of La10Si6O27 is only 3.91 x 10 3 S cm 1.

title: Lanthanum silicate based layered electrolyte for intermediate temperature fuel cell application
abstract: An oxide ion (O2 conducting membrane cell, based on lanthanum silicate oxyapatite (La9.33+xSi6O26+1.5x, LSO) exhibiting low ohmic and polarization resistances in the intermediate temperature region ~873 K) was developed. As a solid electrolyte, highly conductive Mg doped LSO, La9*8(Si5*7Mg0.3)O26.4 (MDLS) modified with another kind of non conductive lanthanum silicate, La2SiO5 was employed. Two kinds of silicate layers were successively spin coated on a Ni MDLS porous anode support, followed by thermal treatment aimed at improving ionic conductivity as well as densification of MDLS through solid state reactive diffusion. In addition, the Gd doped CeO2, (Ce0.9Gd0.1)O1.95 (GDC) electrolyte layer, which plays an important role to prevent a reaction between the electrolyte and cathode materials, was spin coated on the modified MDLS electrolyte. Finally, the cathode layer of porous (La,Sr)(Co,Fe)O3 d was screen printed on the electrolyte layers. The resulting cell obtained from this study showed good fuel cell performance with a maximum power density of 94 mW cm 2 at 873 K, when operated with argon diluted hydrogen and pure oxygen gasses.

title: Influence of cation interdiffusion on electrical properties of doped ceria/lanthanum silicate composite
abstract: La doped ceria (LDC)/lanthanum silicate (LS) and Ga doped ceria (GDC)/LS composites were prepared, and the influence of cation interdiffusion during co firing on the electrical properties of composites was investigated. The electrical conductivity of GDC/LS was lower than that of LDC/LS despite the higher conductivity of GDC compared to LDC. The crystal phases of LDC/LS and GDC/LS were detected as fluorite type cubic ceria (Fm 3 m) and a hexagonal lanthanum silicate (P63/m) respectively, by X ray diffraction (XRD) From energy dispersive X ray spectroscopy (EDS) measurements, it was found that the compositions of the ceria and silicate phases in LDC/LS were nearly stoichiometric after co firing. In contrast, interdiffusion between Gd3+ in the ceria phase and La3+ in the silicate phase was recognized for the GDC/LS. The compositions of the ceria and silicate phases in GDC/LS after co firing were estimated as Gd0.035La0.065Ce0.9O1.95 and La7.910Gd0.423(SiO4)6O0.5, respectively. The Gd3+ substitution for La3+ in the silicate phase in GDC/LS decreased the amounts of 4f site cations. Then, the lattice parameter of the silicate phase decreased. As a result, the decrease in electrical conductivity of GDC/LS is attributed to the decrease in the oxide anion at the 2a site, which is a conduction carrier. It was found from Raman spectroscopy that cation interdiffusion decreased the symmetry mode of the SiO4 tetrahedra for the silicate phase in GDC/LS and brought about increases in the activation energy of electrical conductivity for GDC/LS.

title: Preparation of zinc and alkaline earth metal co doped apatite type lanthanum silicate electrolyte ceramics by combustion method and mechanism of co doping enhanced conductivity
abstract: The amorphous and high purity apatite type lanthanum silicate La9.33A0.2Si5ZnO25.2 (LASZO, A=Ca, Sr and Ba) co doped with zinc and alkaline earth metal has been successfully prepared at 600 degC in 7 9 min by employing the combustion method, along with revealing the combustion thermochemical mechanism. The LASZO ceramics were sintered at 1400 1500 degC after pressing molding. The XRD, IR, SEM and EIS analyses confirm that Zn2+ replaces Si4+ and A2+ replaces LaII3+ along with the lattice volume increasing with the A2+ radius. The conductivity of co doped La9.33Sr0.2(Si5ZnO24)OiOi*0.2 V O at 1073 K is noted as 5.43 x 10 3 S*cm 1, which is higher than undoped, Zn2+ single doped and A2+ single doped ceramics. It is due to the generation of the oxygen vacancy V O by the Zn2+ doping, formation of an oxygen vacancy V O and increased lattice volume leading to a reduced space drag of the oxygen ion transport and A2+ doping increasing the concentration of the interstitial oxygen ions by introducing the additional interstitial oxygen ions Oi* Therefore, the mechanism of co doping driven increment in the conductivity is the oxygen vacancy defect interstitial oxygen concentration lattice volume composite enhancement.

title: Conductivity of Lanthanum Silicate Apatite Derived from Rice Husk
abstract: Effect of difference silica source, namely commersial silica and silica from rice husk, as Si precursor on the synthesis of lanthanum silicate apatite (LSO) have been investigated. The conductivity of LSO was determined by impedance spectroscopy using LCR meter. The conductivity of LSO based on rice husk extraction (s700degC 2.13 10 4 S.cm 1) was ten times lower than that of LSO with commercial silica (s700degC 3.11' 10 5 S.cm 1) Carbon content as an impurity on silica from rice husk extraction is suspected to decrease the homogeneity of its morphology so that it has an impact on its conductivity.

title: Noble metal free catalysts based on apatite type lanthanum silicate for complete toluene combustion
abstract: Noble metal free LaCoO3/La[Formula: see text]Si5CoO[Formula: see text][Formula: see text] Al2O3 catalysts were developed for complete toluene combustion, and their catalytic activities were investigated. The active oxygen supply from the apatite type La[Formula: see text]Si5CoO[Formula: see text] promoter successfully improved the oxidation ability of the LaCoO3 activator, and the highest catalytic activity was obtained for the 10 wt. LaCoO3/20 wt.  Al2O3 catalyst, which oxidized toluene completely at the temperature as low as 300[Formula: see text]C.

title: Templated grain growth of textured lanthanum silicate oxyapatite ceramics