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Thermal behaviour of aluminium-iron-vanadium phosphates precursors of beige ceramic pigments

Other TitlesAluminium; Iron; Vanadium; Phosphates; Thermal decomposition; Kinetics
AuthorsTrobajo, Camino ; Tena, M. A.; Mendoza-Meroño, R.; Alfonso, Belén F.; Huidobro, José A.
Issue Date2019
Citation2nd Journal of Thermal Analysis and Calorimetry Conference (2019)
AbstractModifications of physical properties of solid solutions can be associated with dopant cations and changes in the structure of compounds. Phosphates have a great capacity to form solid solutions and to accept substitutes. The solid solution formation, Al1-xFexPO4, between FePO4 and AlPO4 takes place by the incorporation of Fe3+ ions into the AlPO4 structure for x < 0.5, while for x > 0.5, Al3+ ions are incorporated into FePO4. The calcined samples exhibit a semiconductor trend and at temperatures ≥ 600 °C exhibit a ferromagnetic behaviour at rich FePO4 content. It is due to the decomposition of FePO4 to different phases such as Fe3PO7 and α-Fe2O3. Some structures of phosphates can be used as ceramic pigments in addition to oxides and silicates. The d-d electronic transitions within transition metal ions give rise to many colours. The strong absorbance due to charge transfers is the most important component in the coloration of some solid solutions. The incorporation of small amounts of V(V) ions by substitution of P(V) ions in a structure changes the bond strength and modifies the colour of the materials. Changes in colour can also be obtained by changes in M-O distances and coordination numbers when M is incorporated in different structures. Recently, AlxVyFe1-xP1-yO4 (0.0 ≤ x ≤ 0.3, 0.0 ≤ y ≤ 0.1) compositions were synthesized via the chemical co-precipitation method, and optimal beige materials to work without sample fusion at 1200 °C are obtained from the composition with x = 0.2 and y = 0.05 (Al0.2V0.05Fe0.8P0.95O4). The starting materials were Fe(NO3)3·9H2O, Al(NO3)3·9H2O, H3PO4 and NH4VO3. The stoichiometric amount of NH4VO3, a 0.5 M solution of H3PO4 in water, Fe(NO3)3·9H2O and Al(NO3)3·9H2O were added to water to obtain a final volume of 200 mL. Samples were vigorously stirred for two days at room temperature. Subsequently, an ammonia aqueous solution was added until reaching pH = 10 and precipitation of materials was obtained. All samples were characterized, among others, by powder X-ray diffraction (PXRD), scanning and transmission electron microscopies (SEM, TEM), thermogravimetric analysis (TG-MS-DTG-DSC). In the present work, applying isoconversional methods, we will show the kinetic parameters of the thermal decomposition of the raw materials, previously dried by IR-irradiation.
DescriptionResumen del póster presentado a la 2nd Journal of Thermal Analysis and Calorimetry Conference (JTACC), celebrada en Budapest (Hungría) del 18 al 21 de junio de 2019.
Appears in Collections:(CINN) Comunicaciones congresos
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