Thermal investigation and infrared evolved gas analysis of solid trivalent lanthanide and yttrium α-hydroxyisobutyrates in N_2 and CO_2 atmospheres

摘要

Solid-state Ln(C_4H_7O_3)_3·nH_2O compounds, where Ln stands for trivalent lanthanides or yttrium and C_4H_7O_3~- is α-hydroxyisobutyrate, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), elemental analysis, complexometry and TG-DSC coupled to infrared spectroscopy (FTIR) were used to characterize and to study the thermal behavior of these compounds in CO_2 and N_2 atmospheres. The dehydration of the compounds occurs in a single (La to Nd, Tb to Tm and Y), two (Sm and Gd) and three (Eu) steps in N_2 atmosphere and a single (La, Ce, Tb to Tm and Y), two (Pr, Nd and Gd) and three (Sm and Eu) steps in CO_2 atmosphere. The final residues of the thermal decomposition in N_2 atmosphere for europium to dysprosium, ytterbium and yttrium compounds up to 1000 ℃ were the respective oxides Ln_2O_3 (Ln = Eu, Gd, Tb, Dy, Yb, Y) while for lanthanum, cerium praseodymium, neodymium, samarium, holmium, erbium, thulium and lutetium compounds, the mass loss is still being observed up to 1000℃. In CO_2 atmosphere, the final residue up to 1000 ℃ for all the compounds was the respective oxides, CeO_2, Tb_4O_7 and Ln_2O_3 (Ln = La, Pr to Gd, Dy to Lu and Y).