Synthesis and characterization of spinel pigment CaFe 2 O 4 obtained by the polymeric precursor method R.A. Candeia a, * , M.I.B. Bernardi b , E. Longo c , I.M.G. Santos a , A.G. Souza a a LTM, Department of Chemistry, CCEN, UFPB, Campus I, Cidade Universita ´ria, 58059-900, Joa ˜o Pessoa, Paraı ´ba, Brazil b Crystal Growth and Ceramic Materials Group, USP, 13560-970, Sa ˜o Carlos, SP, Brazil c CMDMC, Department of Chemistry, CCT, UFSCar, Rod. Washington Luis, Km 235, Sa ˜o Carlos, SP, CP 676, 13565-905, Brazil Received 2 June 2003; accepted 30 June 2003 Abstract The CaFe 2 O 4 composition was studied, in order to analyze its physical and chemical behavior, verifying its stability under industrial conditions, when applied as pigments. The characterization was accomplished using thermal analysis, X-ray diffraction (XRD), nitrogen adsorption, scanning electronic microscopy (SEM) and diffuse reflectance. It observed successions exothermics reactions, adequate in events of thermal decomposition of the organic material, reach your stability in 700 jC. The material became completely crystalline at 800 jC. Between 700 and 1100 jC, the color was stabilized, showing an absorption band in the region of 650 to 750 nm, characteristic of the red color. D 2003 Elsevier B.V. All rights reserved. Keywords: Ceramic pigments; Pechini method; CaFe 2 O 4 ; Spinel; Ceramics; Characterization methods 1. Introduction Ceramic materials with spinel structure have been stud- ied for decades, due to its wide applicability as ceramic pigments, magnetic devices, semiconductors, refractories and others. In order to obtain powder-ceramics with high quality, there are important factors—synthesis method deter- mines not only stoichiometric and morphologic control but also physical and chemical properties. Color is an optical property that takes to countless applications. For ceramic tiles, pigments give a stable coloration to a glaze, through a simple mechanical disper- sion in the middle to be colored. The final color of each pigment is due to the addition of a chromophore ion (usually transition metals) into an inert matrix, or this ion may be part of the own matrix, as in the case of ferrites [1]. In this work, a ferrite pigment was synthesized with applicability as pigments, besides magnetic devices, semiconductors, among others. After synthesis, the Fe 2 O 3 /CaO material (consists of calcium ferrite) exhibits a red brick coloration having the spinel structure [2], which usually leads to a high thermal stability. The spinel structure RO.R 2 O 3 , is formed by association of a trivalent oxide (acid character) with a bivalent oxide (alkaline character). Such a ceramic pigment is able to develop stable color in relation to temperature and chemical agents, resisting to the aggressive attacks, special- ly by glaze material during its melting, in other words, the pigment should be insoluble in glazes (substrate) [3]. The chemical synthesis was based on polymeric precur- sors method, which was developed by Pechini. This method consists of formation of a polymeric net starting from a polyhydroxy alcohol and an alpha-hydroxycarboxylic acid, with metallic cations homogeneously distributed throughout the matrix [4,5]. After synthesis, CaFe 2 O 4 physical and chemical behavior was studied, verifying its stability as pigment under industrial conditions. 2. Experimental procedure 2.1. Resin preparation using the polymeric precursors method (PECHINI) The polymeric precursor solution was prepared using the Pechini method, which has been used to synthesize poly- 0167-577X/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0167-577X(03)00563-9 * Corresponding author. E-mail address: gouveia@quimica.ufpb.br (R.A. Candeia). www.elsevier.com/locate/matlet Materials Letters 58 (2004) 569 – 572