[en] The La₂Zr₂O₇ phase was prepared from metal acetylacetonates by a sol-gel route without any intermediate phase formation. X-ray peaks appeared at a temperature as low as 500 degrees C at the positions expected for La₂Zr₂O₇, although they were broad. The crystal structure of La₂Zr₂O₇ was found to be of the fluorite type below 900 degrees C and of the pyrochlore type above 1000 degrees C. The substitution of a small amount of Eu for La was carried out to investigate the crystal structure from the viewpoint of fluorescence, and these results confirmed the formation of fluorite type La₂Zr₂O₇ below 900 degrees C