This paper deals with the growth of coloured zirconium oxide crystals,
cubic stabilized with yttrium oxide. The host material - zirconia - i
s colourless. To generate colourations minor concentrations of 3d- and
4f-elements are incorporated into the lattice. The resulting colours
are dependent on the ions' valence and the local crystal symmetry. Bot
h, the possibility to change the ions' Valence by heat treatment, and
the possibility to change the local crystal symmetry by alteration of
the starting yttria concentration, are discussed in the following.