Zn 0.97 M 0.03 O (M 5 Co, Fe, and V) pigments: thermal, structural, and optical characterization T. M. Mila ˜o • J. F. A. Oliveira • V. D. Arau ´jo • M. I. B. Bernardi Received: 18 August 2010 / Accepted: 13 October 2010 Ó Akade ´miai Kiado ´, Budapest, Hungary 2010 Abstract Zinc oxide is a widely used white inorganic pigment. Transition metal ions are used as chromophores and originate the ceramic pigments group. In this context, ZnO particles doped with Co, Fe, and V were synthesized by the polymeric precursors method, Pechini method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of decomposition temperatures due to different exothermal events, which were identified as H 2 O elimination, organic compounds degradation and phase formation. The samples were structurally characterized by X-Ray diffractometry revealing the formation of single phase, corresponding to the crystalline matrix of ZnO. The samples were optically characterized by diffuse reflectance measurements and colorimetric coordinates L*, a*, b* were calculated for the pigment powders. The pigment powders presented a variety of colors ranging from white (ZnO), green (Zn 0.97 Co 0.03 O), yellow (Zn 0.97 Fe 0.03 O), and beige (Zn 0.97 V 0.03 O). Keywords ZnO  Dopants  Pechini method  Pigments Introduction Inorganic pigments are traditionally based on transition metal compounds. Research on ceramic pigments has lately been dedicated to improve traditional colored systems from an environmental point of view and maintaining their coloring properties and technological requirements [1]. Attempting to achieve zero emissions and waste, as well as a reduction of energy costs, a good understanding of the reaction mechanisms depending on the chemical compo- sition is required. Moreover, the product performance must meet the growing social demands with regard to safety, sustainability, and minimal environmental impact [1]. Zinc oxide (ZnO) has a wide direct band gap of 3.37 eV at room temperature and a large exciton binding energy of about 60 meV with the electrical and optical properties of a II–VI semiconductor. It has useful characteristics, such as excellent thermal and chemical stability, a large piezoelec- tric constant, and an easily modified electric conductivity [2]. In ZnO, the Zn atoms are tetrahedrally coordinated to four oxygen atoms, where Zn d electrons hybridize with the oxygen p electrons. The interest in determining electrical and optical properties of doped bulk ZnO is motivated by the need to develop an understanding of the material response to impurities introduced by doping [3]. Zinc oxide (ZnO) has attracted attention because of the wide range of applications such as solar cells, luminescent, electrical, and acoustic devices, as well as chemical sensors [4], varistors and pigment in paints [3]. In recent years, many techniques and methods have been investigated for the obtention of ZnO nanostructures, such as solvothermal method [5], sol–gel technique [3], solid- state reaction [6], and Pechini method [7]. Lima et al. [8] mention the different methods, such as physical and chemical vapor deposition, metal organic vapor-phase T. M. Mila ˜o (&)  J. F. A. Oliveira Departamento de Quı ´mica, UFSCar—Universidade Federal de Sa ˜o Carlos, Rodovia Washington Luiz, Km 235, Sa ˜o Carlos, SP 13565-905, Brazil e-mail: thismilao@gmail.com V. D. Arau ´jo  M. I. B. Bernardi Instituto de Fı ´sica de Sa ˜o Carlos, USP—Universidade de Sa ˜o Paulo, Av. Trabalhador Sa ˜o-carlense, 400, Sa ˜o Carlos, SP 13560-970, Brazil 123 J Therm Anal Calorim DOI 10.1007/s10973-010-1107-z