Published on the Journal of Solid State Chemistry, 179 (2006) 233-246 Copyright © 2006 Elsevier Ltd. All rights reserved. doi: 10.1016/j.jssc.2005.10.032 1 Zirconium Titanate Ceramic Pigments: Crystal Structure, Optical Spectroscopy and Technological Properties M. Dondi 1 , F. Matteucci 1 , G. Cruciani 2 1 Institute of Science and Technology for Ceramics (ISTEC – CNR), Via Granarolo 64, 48018 Faenza, Italy 2 Department of Earth Sciences, Via Saragat 1, University of Ferrara, 44100 Ferrara, Italy Abstract Srilankite-type zirconium titanate, a promising structure for ceramic pigments, was synthesized at 1400°C following three main doping strategies: a) Z rTi 1-x A x O 4 , b) ZrTi 1-x-y A x B y O 4 and c) Zr 1-x C x TiO 4 where A = Co, Cr, Fe, Mn, Ni or V (chromophores), B= Sb or W (counterions) and C = Pr (chromophore); x=y=0.05. Powders were characterized by XRD with Rietveld refinements and DRS in the UV-Vis-NIR range; technological properties were appraised in several ceramic matrices (frits, glazes and body). Zirconium titanate can be usefully coloured with first row transition elements, giving green and greenish yellow (Co and Ni); orange-buff (Cr and V); tan-brown hues (Mn and Fe). In industrial-like synthesis conditions, a disordered structure as (Zr,Ti)O 2 , with both Zr and Ti randomly distributed in the octahedral site, is achieved. Doping with chromophores and counterions induces unit cell dimensions variation and causes an oversaturation in zirconium oxide. Optical spectroscopy reveals the occurrence of Co 2+ , Cr 3+ , Fe 3+ , Mn 2+ , Mn 3+ , Ni 2+ , V 3+ and V 4+ . The zirconium titanate pigments fulfil current technological requirements for low temperature applications, but exhibit a limited chemico-physical stability for higher firing temperature and in chemically aggressive media. Key-words: ceramic pigments, crystal structure, order-disorder, optical spectroscopy, zirconium titanate, srilankite 1. Introduction The zirconium titanate solid solution with Zr:Ti molar ratio ranging from 1:1 to 1:2 is the only stable binary compound in the Zr-Ti-O system [1]. Two structural modifications are known: high temperature disordered Zr 1-x Ti x O 4 and low temperature ordered ZrTiO 4 [2-4]. The high T disordered phase crystallizes in the orthorhombic α-PbO 2 structure (space group Pbcn; setting of the unit cell: a⋅b⋅c=4.7⋅5.5⋅5.0 Å; Zr and Ti randomly distributed in the octahedral site with 0.41<X Ti <0.53 at 1400°C [3-4]), is stable above 1100°C and persists metastably at lower temperature because the ordering process is sluggish, being associated with a reconstructive transformation and driven by the respective preferences of the Zr and Ti ions for 8(7)-fold and 6-fold coordination respectively [3-4]. There are two types of ordered structures with different stoichiometries both stable below 1200°C [5-6]: a) stacking of two layers of distorted Zr sites plus two layers of octahedral Ti sites alternated along the axis a, giving rise to a doubling of the parameter a (cell setting: a⋅b⋅c=9.6⋅5.3⋅5.0 Å) with respect to the disordered phase; this ordering scheme is consistent with the formula ZrTiO 4 (Zr:Ti ratio = 1:1; X Ti = 0.5);