ORIGINAL ARTICLE Synthesis and characterization of ferrimagnetic glass-ceramic frit from waste Isabel Gonz alez-Trivi ~ no 1 | M onica Ben  ıtez-Guerrero 1 | Juan Carda Castell o 2 | Bel  en Moreno 1 | Jos e Pascual-Cosp 1 1 Departamento de Ingenier  ıa Civil, de Materiales y Fabricaci on, Universidad de M alaga, M alaga, Spain 2 Departament de Qu  ımica Inorg anica i Org anica, Universitat Jaume I, Castell o de la Plana, Castell o, Spain Correspondence Isabel Gonz alez-Trivi~ no Email: m.isabel_gt@yahoo.com Abstract The large amount of generated waste determines the importance of their valoriza- tion. Red mud is the residue of the Bayer process, which stored cumulative value raises 2.7 Bt. This paper describes an easy way to produce a ferrimagnetic glass- ceramic frit, using bauxite residue, fly ash and glass cullet as raw materials. The synthesized frit consists of faceted and dendritic agglomerated crystals of mag- netite and titanomagnetite embedded in a glass matrix, which exhibits a saturation magnetization (M S ) of 6.3 emu/g, a remanent magnetization (M R ) of 2.7 emu/g and a coercive field (H C ) of 347 Oe. Furthermore, it presents Vickers hardness value of H V = 5.55 Æ 0.16 GPa and fracture toughness value of K IC = 1.64 Æ 0.34 MPaÁm 1/2 . KEYWORDS glass-ceramics, hardness, magnetic materials/properties, transmission electron microscopy 1 | INTRODUCTION The large amount of generated waste has caused and is still causing serious environmental problems. Promising ways to reuse these residues are by ceramization and, specially for hazardous waste, vitrification. Much research has been focused on utilizing different waste as raw materials to pro- duce glass and glass-ceramics in order to reduce fabrication costs and remove contaminating residues, thus generating eco-friendly products. 1-4 A great number of these works were dedicated to enhance the mechanical properties for structural applications. However, increasing the value of the glassy or glass-ceramic product by inducing or control- ling valuable functionalities is desirable. A magnetic glass-ceramic is a special composite consti- tuted by magnetic nanocrystals embedded in a vitreous matrix. Its importance arises from the great potential appli- cations which include magnetic storage devices, contrasting agents for magnetic resonance imaging, biodetection and microwave devices, among others. 5 Iron oxides, as hematite and magnetite, are the most investigated magnetic compounds in glass-ceramic system and iron-rich waste have been profusely analyzed as raw materials so. 6 Red mud or bauxite residue generated during the Bayer process is an alkaline solution with pH between 10 and 13, which represents a serious environmental problem. 7 Direct sea discharge of red mud has been usual for years, so differences in the nature of the seabed about con- trol locations have been observed. 8,9 The main disposal method today consist in the storing of the residue in huge ponds with low solids content. The annual production of residue is estimated at 120 Mt and the global inventory ascends over 2.7 Bt. 10 The large amount of sludge gener- ated during the process and the cumulative value of this determine the importance of valorization. Researches regarding the use of red mud include metallurgic processes or catalysis in waste treatment. 11,12 But it is by far its use in the manufacture of construction elements the most extended option, as this is an industry that needs large amounts of raw materials. 13,14 As well, significant researches are carried out on the production of glasses and glass-ceramics from bauxite residue. 15,16 Coal fly ash is an industrial waste produced during the combustion of coal for energy generation. The annual Received: 7 November 2017 | Accepted: 14 December 2017 DOI: 10.1111/ijac.12850 Int J Appl Ceram Technol. 2018;15:775–782. wileyonlinelibrary.com/journal/ijac © 2017 The American Ceramic Society | 775