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- Author or Editor: J. Šiftar x
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Double rare earth(III) monomethylammonium sulfates with general empirical formula CH3NH3Ln(SO4)2·3H2O (Ln = La-Er and Y) were synthesized and examined by X-ray powder diffraction, TG, DTG and DTA in the temperature range from 25° to 700°C, and chemical analysis. It was found that these compounds are isomorphous and decompose to rare earth sulfate at 700°C.
Abstract
The title compounds were studied by thermogravimetry and differential thermal analysis in flowing dry air, in the temperature range 25–500°C, at a heating rate of 4 deg·min−1. Thermal analysis revealed two principal effects: dehydration, with the probable formation of a monohydrate, and oxidation of the oxalate ion at around 400°C.
Abstract
Oxalates of La(III), Ce(III), Pr(III), Nd(III) and Sm(III) with the hydrazinium cation with the general formulae (N2H5)4Ln2(C2O4)57H2O (Ln=La3+, Ce3+, Pr3+) and N2H5Ln(C2O4)2·3.5H2O (Ln=Nd3+, Sm3+) were synthesized. The thermal decompositions of these compounds take place in three stages: thermal dehydration at 65–100°C, exothermic decomposition of the N2H4 at 230–260°C, and oxidation of the oxalate ion.
Abstract
On the basis of uniform methodics, oxalatometallates of rare earths(III) with sodium, were synthesized. The compounds were obtained by adding saturated solution of sodium oxalate to 1 M solutions of Ln(NO3)3 in a molar ratio Na2C2O4/Ln3+ not lower than 5. X-ray powder diffraction photographs were used for the classification of the isolated compounds into five, internally isostructural groups.
Synthesis and dehydration of double oxalates of rare earths(III) with some monovalent metals
II. Investigations of RbLn(C2O4)2·nH2O
Double oxalates of rare earths(III) and rubidium with the general formulae RbCe(C2O4)2 4.5H2O, RbLn(C2O4)24H2O (Ln=Yb, Lu), RbLn(C2O4)2·3.5H2O (Ln=La, Pr-Dy), and RbLn(C2O4)2·3H2O (Ln=Ho, Er, Tm, Y) were synthesized. They were characterized by chemical analysis, TG, DTG and DSC over the temperature interval 20–500‡C and X-ray powder diffraction examination. At the chosen final temperature (500‡C), either oxide (Ln2O3) or basic carbonate Ln2O2CO3) and Rb2CO3 were obtained, depending on the rare earth(III) element. On the basis of the X-ray diffraction patterns, the isolated compounds can be divided into five isostructural groups.
Abstract
When reaction mixtures of rare earth(III) sulphates and tetramethylammonium sulphate in molar ratios of from 1∶4 to 1∶12 were evaporated at ambient temperature and the concentrated reaction mixture was treated with ethanol, double sulphates with general empirical formula (CH3)4NLn(SO4)22H2O (Ln=Ho−Lu and Y) were obtained as reaction products. The crystalline products were identified by quantitative analysis, X-ray powder diffraction patterns and TG, DTG and DTA analysis. They were found to be isostructural. Their thermal decomposition took place in three stages. The temperature range of the dehydration mainly decreased from Ho to Lu. The thermal decomposition in the second and third stages occurred with many thermal events. As final product, Ln2O(SO4)2 was obtained.
Synthesis and dehydration of double oxalates of rare earths(III) with some monovalent metals
I. Synthesis and thermal behaviour of KLn(C2O4)2·nH2O
The synthesis of double oxalates of rare earths(III) and potassium with empirical formulae K4Ln2(C2O4)5·10H2O (Ln=La, Ce) and KLn(C2O4)2· nH2O (wheren=4 for Pr-Dy andn=4.5 for Ho-Lu, Y) is described. The compounds obtained were studied by TG, DTG and DTA over the temperature interval 25–500‡C and by X-ray powder diffraction and chemical analysis. Three structurally different groups were recognized. It was found that either rare earth oxide or basic carbonate (Ln2O2·CO3) and potassium carbonate were obtained as final product at 500‡C, depending on the rare earth element. The thermal decomposition takes place in two well-resolved stages.
