Cerium oxide for sunscreen cosmetics

Ultrafine particles of Mn+-doped ceria (Mn+ = Mg2+, Ca2+, Sr2+, Ba2+, y(3+), La3+, Nd3+, Sm3+, Eu3+, Tb3+) for UV filter were prepared via soft solution chemical routes at 40degreesC. X-ray diffraction revealed that the prepared doped particles had the cubic fluorite structures although peak positions changed depending on the kind and amount of doped metal ion. Doping with 20 mol% Ca2+ and 20 mol% Zn2+ resulted in extremely decreasing the particle size (2-4 nm) and the catalytic activity of ceria for oxidation of castor oil. Ca2+-doped cerium dioxide showed excellent UV absorbing effect and transparency in the visible ray region compared with undoped cerium dioxide. (C) 2003 Elsevier Science (USA). All rights reserved.