Sol-gel and PLD preparation of the lanthanum gallate-based mixed ionic-electronic conducting oxides
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1126-S01-09
Sol-gel and PLD preparation of the lanthanum gallate-based mixed ionic-electronic conducting oxides Natalia V. Golubko1, Galina M. Kaleva1, Yuliana E. Roginskaya1, Sergey P. Kabanov1, Alexander K. Avetisov1, Gunnar Suchaneck2 and Ekaterina D. Politova1 1 L.Y. Karpov Institute of Physical Chemistry, Vorontsovo pole, 10, 105064, Moscow, Russia 2 TU Dresden, Solid State Electronics Lab, 01062 Dresden, Germany ABSTRACT Ionic and mixed conducting oxides (La0.9Sr0.1)[(Ga1-xFex)0.8Mg0.2]O3-y (I) and (Sr1.8La0.2)(GaFe)O5.1 (II) with the perovskite and brownmillerite structures, respectively, have been prepared in forms of dense bulk ceramics and ceramic coatings by the sol-gel method. Thin films II have been grown by the pulsed laser deposition method on single crystal MgO (100) and Si (100), fused silica, and stainless steel substrates. The films grown under optimal process conditions were single-phase and homogeneous, with a high degree of preferential orientation. The structure and microstructure of the ceramic coatings have been studied by X-ray diffraction and scanning electron microscopy. INTRODUCTION Oxides with high ionic conductivity comprise the subject of intense studies as potentially attractive materials for a variety of electrochemical devices [1]. Solid solutions based on lanthanum gallate, LaGaO3, are believed to be among the most promising ionic conductors in the group of perovskite oxides [2]. Doping of lanthanum gallate with strontium and magnesium cations leads to the formation of solid solutions that offers excellent ionic conductivity at temperatures below 1200 K and high stability in a wide range of oxygen partial pressures, from 105 to 10-17 Pa. A starting point of dense ceramic coatings and thin films are submicron powders. One of the most attractive processes for the preparation of submicron powders is the sol-gel synthesis, a process in which oxide particles are precipitated from various homogeneous aqueous or nonaqueous solutions. Starting from molecular precursors in the sol, a polymer-like, gelatinous network (gel) is formed by partial evaporation of the liquid or addition of a suitable initiator which can then be dehydrated and calcined to obtain submicron ceramic powders or thin films. The main advantages of sol-gel synthesis are the ability to prepare homogeneous powders of high purity and the possibility to reduced sintering temperature. Thin films of multicomponent perovskite oxide ceramics can be produced by the pulsed laser deposition (PLD) method as well. In this case, a stoichiometry transfer between target and substrate is obtained with most materials [3]. Previously, we have determined the stability limits and structure parameters of lanthanum-gallate-based solid solutions, (La,Sr)(Ga,Mg,M)O3-y with M = Fe, Ni, Cr, and Mn, prepared by conventional solid-state reactions [4-8]. The structure parameters and microstructure of the perovskite solid solutions were determined, the composition ranges with the highest oxygen permeability promising for the development of oxygen sep
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