126 Interceram 02/2013 Building Materials 1 Introduction Transition metal glasses, such as iron-rich glasses, are of considerable interest in me- dicine, electro-ceramics, optical ceramics, structural ceramics, waste sectors, as well as in geology and basic sciences. These glasses are well known for their interesting properties, which depend strongly on com- position, synthesis method and thermal treatments [1–10]. In the floor and wall tile manufacturing industry, iron oxide-rich glasses have been used for the development of glazes with metallic and aventurine ef- fect, using compositions rich in P 2 O 5 and Fe 2 O 3 [11–12]. The wide range of proper- ties that such glasses display provides them with great potential for the development of numerous technological applications like semiconducting glazes for antistatic or ra- diant flooring and for electrical insulators [13–17]. The semiconducting properties in these glasses are a result of a mechanism known as polaron hopping, caused by the transfer of electrons between the same metallic ion in different oxidation states (e.g. from Fe 2+ to Fe +3 ). This conduction mechanism is known to be present in iron-rich glasses and in crystalline phases like magnetite [18]. In this sense, the SiO 2 –CaO–Fe 2 O 3 glass system was initially studied for its magnetic properties, which are useful for biomedical and electronic applications. In numerous studies this sys- tem has shown the ability to vitrify or form high-temperature eutectics and to crystal- lize phases such as β-CaO·SiO 2 (wollasto- nite), zinc ferrites, magnesium ferrites, apatite in magnetic clusters, magnetite (Fe 3 O 4 ) and γ-Fe 2 O 3 , hematite (α-Fe 2 O 3 ) and cristobalite [1, 2, 7–10]. Taking advan- tage of magnetite’s ease of crystallization in iron-rich oxide glass systems, previous Glasses in the Fe 2 O 3 –SiO 2 –CaO system are potential candidates for many technological applications due to their ferrimagnetic and semiconductive properties, which have been extensively studied; in this sense, the effect of adding different melting additives like Li 2 O, B 2 O 3 , in this glass system on frits and glazes with 30–40 mass-% of Fe 2 O 3 was studied. Ceramic frits were melted at different temperatures with subsequent cooling in water. Samples were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis and thermogravimetry (DTA, TG) and by heating microscopy. Finally, frits were applied as glazes on ceramic tiles to evaluate their capacity to adapt to the tile productive process. The frits showed low to high homogeneity (depending on the fusion temperature) and oxidation phenomena. High temperature fusion led to the crystallization of magnetite during cooling. Glaze porosity was observed after heat treatment with the presence of anorthite and hematite as crystalline phases in glazes. AbstrAct G. Rosales-Sosa*, T. Poirier*, J. Lira-Olivares*, J.B. Carda-Castelló** Effect of Fluxing Additives in Iron-rich Frits and Glazes in the Fe 2 O 3 –SiO 2 –CaO–Al 2 O 3 System Gustavo A. Rosales-Sosa earned a Materials Engineering degree from the Simón Bolívar University of Caracas (Venezuela) in 2008 and is completing his M.Sc. degree through collaboration between his university and Jaume I University in the field of glass and glass-ceramics for the tile industry. He has been a Member of the Center for Surface Engineering at Universidad Simón Bolivar in Cara- cas since 2007, where he does research in the field of glass science and technology, wear and failure analysis of metallic alloys. E-Mail: gustavorosales@gmail.com the Authors Thierry Poirier earned a Ph.D. in Ceramic Materials and Surface Treatment at University of Limoges in 2000. He is Titular Professor at Universidad Simón Bolívar in and a Member of the Surface Engineering Group in the Materi- als Science Department, where he pursues his research interests in ceramic processing, concrete, glass-ceramics and thermal spraying. He has authored 23 articles in na- tional and international journals, and contributed to 40 conferences and meetings. E-Mail: tpoirier@usb.ve The main author, Juan B. Carda-Castelló, earned a Ph.D. in Chemistry and became Full Professor at Jaume I Uni- versity of Castellón in 1993. He is a Cathedratic Profes- sor in Inorganic Chemistry in the Department of Inorgan- ic and Organic Chemistry and Co-founder of the Solid State Chemistry Group, where he pursues his research interests. The focus of his extensive research activities and studies is on synthesis, properties and novel appli- cations of ceramic materials. He has authored more than 150 articles in na- tional and international journals, more than 400 scientific national and in- ternational contributions, and multiple books in the field of chemistry and materials. E-Mail: carda@qio.uji.es Joaquín Lira-Olivares, Emeritus Professor at Universidad Simón Bolívar in Caracas (Venezuela), is Director of the Center for Surface Engineering at the same university. He has published more than 100 articles in indexed jour- nals and proceedings and has participated in the devel- opment of materials science books. His contributions to science and technology in the last 30 years have concen- trated on surface science, wear, coatings design and characterization. His recent invited publications are “Testing” of coatings for ASM (2001) and “Designing a Surface for Endurance: Coatings Deposi- tion Technologies” in the Handbook of Metallurgical Process Design, Marcel Dekker Inc. (2004). magnetite, frits, ferrimagnetism, glazes, iron Interceram 62 (2013) [2] Keywords * Department of Materials Sciences, Universidad Simón Bolívar, AA89000, Caracas 1080A (Venezuela) ** Department of Inorganic and Organic Chemistry, Universidad Jaume I, Castellón (Spain)