Environmental optimisation of blue vanadium zircon ceramic pigment

Thermal treatment and the addition of V2O5 and of different mineralising ag ents (NaF, NaCl and borax) have been optimised in terms of colour yield (L* a*b*) and of environmental considerations (atmospheric emissions and vanadi um leachates). The formation of different reaction intermediates depending on mineraling agent (ZrV2O7 for no mineraliser, NaVO3 and/or sodium-vanadiu m bronzes for added sodium halides, and a borosilicate vitreous phase for a dded borax) proves be important for the pigment synthesis, lending to diffe rent zircon yields and to different colour performance in the fired pigment s. The composition (ZrSiO4)(V2O5)(0.19) (NaF)(0.05)(NaCl)(0.10) has been fo und to be the optimal environmentally (firing loss = 5.8%, vanadium leached = 284 ppm and b* = -16.4), though the non-mineralised composition (with 0. 19 mol of V2O5 per zircon formula weight) also performs well. (C) 1999 Publ ished by Elsevier Science Limited. All rights reserved.