Thermal analysis (TG-DSC, DSC-microscopy and EGA) and characterization of heavy trivalent lanthanides and yttrium isonicotinates

Author(s)

Nunes, W. D. G. ^{[1, 2]} ; Teixeira, J. A. ^[1] ; do Nascimento, A. L. C. S. ^[1] ; Ekawa, B. ^[1] ; Ionashiro, M. ^[1] ; Caires, F. J. ^{[1, 3]}

Affiliation

^[1] Univ Estadual Paulista UNESP, Inst Quim, Araraquara, SP - Brazil

^[2] Inst Fed Educ Ciencia & Tecnol Rondonia, Campus Guajara Mirim, Guajara Mirim, RO - Brazil

^[3] Univ Estadual Paulista Unesp, Fac Ciencias, Bauru, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY; v. 138, n. 1, p. 309-319, OCT 2019.
• Web of Science Citations: 0

Abstract

The trivalent lanthanide isonicotinates were synthesized to obtain stoichiometry Lu(IN)(3) and Ln(IN)(3).2H(2)O (Ln = Tb to Lu, and Y; IN = isonicotinate). A deep study of the thermal behavior in oxidant (air) and inert (N2) atmospheres was carried out using the following thermoanalytical techniques: simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), differential scanning calorimetry (DSC) and evolved gas analysis (EGA by TG-DSC-FTIR). From these results, it was possible to determine that dehydration occurs in a single step and the thermal decomposition of the anhydrous compounds occurs in one or two (air), and two or three steps (N-2). The final residues of thermal decomposition were Tb4O7 and Ln(2)O(3) (Ln = Dy to Lu, and Y) in air atmosphere, while in N-2 atmosphere the mass loss is still being observed up to 1000 degrees C. The identified gaseous products evolved during the thermal decomposition in dynamic dry air and nitrogen atmospheres were water, CO2, pyridine and CO. From these thermoanalytical data, it was possible to propose a general equation of thermal decomposition of these compounds in the N-2 atmosphere. DSC curves of Tb and Ho compounds presented endothermic peaks corresponding to a reversible phase transition, confirmed by powder X-ray diffractometry (XRD), not previously reported. In addition, infrared vibrational spectroscopy (IR) suggests the coordination through carboxylate as bridging bidentate ligand toward the heavy trivalent lanthanides metals. This paper is complementary to our previous study involving the series of light trivalent lanthanides isonicotinates. (AU)

• FAPESP's process: 18/24378-6 - Synthesis, characterization and thermoanalytical study of Valsartan, Candesartan Cilexetil and Olmesartan medoxomil co-crystals
• Grantee: Flávio Junior Caires
• Support Opportunities: Regular Research Grants
• FAPESP's process: 17/14936-9 - Preparation, characterization and thermoanalytical studies of heterogeneous catalysts of double selenates of Mg/Co and Mg/Cu in biodiesel production using different oils
• Grantee: Massao Ionashiro
• Support Opportunities: Regular Research Grants