Abstract. Ion exchange of LaCl 3 and ZrOCl 2 aqueous solutions with anion-exchanger AV-17-8 was used to synthesize finely dispersed hydrosol of amorphous lanthanum zirconate La 2 Zr 2 O 7 . Heat treatment of dried La 2 Zr 2 O 7 hydrosols at 700ºC and 1100ºC resulted in the formation of powders with fluorite and pyrochlore type structures, respectively. Epitaxial La 2 Zr 2 O 7 films were obtained on SrTiO 3 (001) single crystals. The substrate has an influence on the lanthanum zirconate crystal orientation, as well as strong inhibitory effect on sintering processes.
IntroductionLanthanum zirconate La 2 Zr 2 O 7 has a cubic pyrochlore structure [1] and is highly thermostable. It is used in superconductors of the second generation as thin buffer layers since its lattice parameters match those of YBCO (0.5 %), and also because it provides a good barrier against oxygen diffusion [2,3]. Lanthanum zirconate (LZO) buffer layers are mainly prepared by the alkoxide sol-gel route [2,4], MOD [5], and CSD [3,6] methods from solutions of La and Zr organic compounds in organic solvents, for example, lanthanum isopropoxide and zirconium n-propoxide dissolved in 2-methoxyethanol [2,4] and lanthanum (III) and zirconium (IV) 2,4-pentadionate, that are transformed into respective propionate, when dissolved in the propionic acid [3,5]. Water-based solutions, containing metal acetates, acetic acid, triethanolamine, and ammonium hydroxide were proposed in order to avoid organic solvents [7]. We have developed the ion exchange method for synthesis of amorphous lanthanum zirconate hydrosol free from organic components. In this paper we report the synthesis route and properties of the product obtained.
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