The opto-ceramics and optical elements of the present invention are transmissive to visible light and/or to infrared radiation. They consist of a crystal combination in which individual crystallites have a cubic structure of the type Y.sub.2O.sub.3 and are made from In.sub.2O.sub.3 or a mixture of oxides of the type X.sub.2O.sub.3 in which X=Y, Lu, Sc, Yb, In, Gd, or La. Also mixtures of X.sub.2O.sub.3 with oxides having different stoichiometries, such as zirconium and hafnium oxide, are possible, as long as the cubic structure of the opto-ceramic is maintained. The optical elements prepared from the opto-ceramics are particularly suitable for mapping optics, such as objectives having reduced chromatic aberrations, in particular with approximately apochromatic mapping behavior. The optical elements of the present invention may be used in lens systems in combination with lenses of glass, but also with other ceramic lenses.