PHYSICOCHEMICAL PROPERTIES OF LA-ZR-O AND CE-ZR-O SYSTEMS OBTAINED BYCOPRECIPITATION

A study has been made of the effect of the conditions of preparation a nd the nature and ratio of components on the formation of phase compos ition and specific surface of oxide compounds R-Zr-O, where R is La or Ce, which are obtained by codeposition. The deposition conditions (pH , temperature) do not have a significant effect on these properties; t he nature and concentration of the R2O3 is the decisive factor. Proces ses of dehydration and formation of oxide phases in lanthanum-zirconiu m materials are not complete until temperatures greater-than-or-equal- to 700-degrees-C; a compound with a pyrochloric structure - La2Zr2O7 - is present in samples containing 33.3 less-than-or-equal-to La2O3 < 9 0 mole %. The cerium-zirconium materials even in the stage of drying i n air are oxide compositions with the structure of CeO2. The surface o f the lanthanum-zirconium materials is minimum when the concentration of La2O3 is almost-equal-to 33.3 mole %; it remains unchanged at 110-7 00-degrees-C. The surface of the cerium-zirconium materials decreases monotonically with an increase of the concentration of Ce2O3 at 110-de grees-C and is practically independent of the composition in the 400-7 00-degrees-C interval.