Thermal decompositions of lanthanum and lanthanide salts of sebacic acid

The conditions of thermal decomposition of La, Ce(III), Pr(III), Nd, Sm(III), Eu, Gd, Tb(III), Dy, Ho, Er, Tm, Yb and Lu sebacates have been studied. When heated in air atmosphere, the sebacates of La and lanthanides with general formula Ln₂(C₁₀H₁₆O₄)₃·nH₂O, wheren=6?24, lose some crystallization water molecules in one or two steps at 323–343 K and are then dehydrated and decomposed simultaneously to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The oxides are formed over the range of temperature 783 K (CeO₂)?1073 K (Nd₂O₃).     

Thermal decompositions of light lanthanide aconitates

The conditions of thermal decomposition of Y, La, Ce(III), Pr, Nd, Sm, and Gd aconitates have been studied. On heating, the aconitate of Ce(III) loses crystallization water to yield anhydrous salt, which then is transformed in to oxide CeO₂. The aconitates of Y, Pr, Nd, Sm, Eu and Gd decompose in three stages. First, aconitates undergo dehydration to form the anhydrous salts, which next decompose to Ln₂O₂CO₃. In the last one the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ is accompanied by endothermic effect. Dehydration of aconitate of La undergoes in two stages. The anhydrous complex decomposes to La₂O₂CO₃; this subsequently decomposes to La₂O₃.     

Studies on the Thermal Decomposition of Rare Earth Caproates

The thermal decomposition of rare earth caproates with general formula Ln(C₅H₁₁COO)₃ nH₂O, (where Ln=Y, La-Pr, n=l; Ln=Nd-Er, n=2; Ln=Tm-Lu, n=3) were studied in an air atmosphere. On heating, the hydrated caproates are dehydrated in one step and then the anhydrous complexes decompose to the oxides (Ln₂O₃, Pr₆O₁₁) with formation of the intermediate Ln₂O₂CO₃ (La, Pr-Gd) or directly to the oxides Ln₂O₃, CeO₂, Tb₄O₇(Y, Ce, Tb-Lu). Caproates of rare earth elements are liquefied during dehydration.     

Spectroscopic and Thermal Studies of Rare Earth Element 4-Methylphthalates

Complexes of lanthanide(III) (La-Lu) and Y(III) with 4-methylphthalic acid were prepared and their IR spectra, solubility in water at 295 K and thermal decomposition were investigated. Rare earth complexes were obtained as solids with a 2:3 ratio of metal to organic ligand. COO^– groups in the prepared complexes act as bidentate chelating and bidentate bridging. During heating they are dehydrated in one (La-Tm) or twosteps (Yb, Lu and Y) and then decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectral and Thermal Studies of Rare Earth Element 3-methylglutarates

Conditions for the formation of rare earth element (Y, La–Lu) 3-methylglutarates were studied and their quantitative composition and solubilities in water at 293 K were determined (10^–2 mol dm^–3). The IR spectra of the prepared complexes with general formula Ln₂(C₆H₈O₄)₃ nH₂O (n=3–8) were recorded and their thermal decomposition in the air were investigated. During heating the hydrated 3-methylglutarates are dehydrated in one step and next anhydrous complexes decompose to oxides Ln₂O₃ with intermediate formation Ln₂O₂CO₃ (Y, La, Nd–Gd) or directly to the oxides, Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ (Ce, Pr, Tb–Lu). This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal and spectral studies of rare earth element 3-methoxy-4-methylbenzonates

3-Methoxy-4-methylbenzoates of Y(III) and lanthanide(III) (La-Lu) were prepared as crystalline compounds with molar ratio of metal to organic ligand of 1.0:3.0 and general formula Ln(C₉H₉O₃)3·nH₂O, where n=2 for Y, La-Er and n=0 for Tm-Lu. IR spectra of the prepared complexes suggest that carboxylate groups are bidentate chelating. During heating dihydrated complexes lose crystallization water molecules in one (Y, La, Pr-Er) or two steps (Ce) and then all the anhydrous complexes decompose directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇.Vadim Mamleev is grateful to Region Nord-pas-de-Calais (France) for financial support and to laboratory PERF of ENSCL for its kind invitation to continue the joint work on thermal analysis.     

Thermal decomposition of rare earth element enanthates

The conditions of formation of Y, La and lanthanide (from Ce(III) to Lu) enanthates were worked out, their composition and their solubilities in water at 291 K were determined, and the conditions of their thermal decomposition were studied. They were prepared as crystalline solids with general formula Ln(C₇H₁₃O₂)₃·nH₂O, wheren=2–10. On heating, they decompose in two or three steps. They first lose some water molecules and then decompose to the oxides directly (salts of Y and heavy lanthanides) or via the intermediate formation of Ln₂O₂CO₃ (salts of La, Pr, Nd, Sm and Eu). Only yttrium enanthate dihydrate loses 2 water molecules on heating to form an anhydrous complex, which decomposes directly to Y₂O₃. The temperatures of dehydration are similar for all complexes (323–343 K), while the temperatures of oxide formation vary irregularly from 823 K for CeO₂ to 1078 K for La₂O₃.     

Thermal decomposition of lanthanide(III) and Y(III) 3,4,5-trihydroxybenzoates: Preparation, properties

Complexes of lanthanides(III) (La-Lu) and Y(III) with 3,4,5-trihydroxybenzoic acid (gallic acid) were obtained and their thermal decomposition, IR spectra and solubility in water have been investigated. When heated, the complexes with a general formula Ln(C₇H₅O₅)(C₇H₄O₅)·nH₂O (n=2 for La-Ho and Y: n=0 for Er-Lu) lose their crystallization water and decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁, and Tb₄O₇, except of lanthanum and neodymium complexes, which additionally form stable oxocarbonates such as Ln₂O₂CO₃. The complexes are sparingly soluble in water (0.3·10^–5–8.3·10^–4 mol dm^–3).This revised version was published online in November 2005 with corrections to the Cover Date.     

Solid-state 2-methoxybenzoates of light trivalent lanthanides

Solid-state LnL₃ compounds, where L is 2-methoxybenzoate and Ln is light trivalent lanthanides, have been synthesized. Thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy and elementary analysis were used to characterize and to study the thermal behaviour of these compounds. The results led to information on the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds. On heating these complexes decompose in three (Ce, Pr) or five (La, Nd, Sm) steps with the formation of the respective oxide: CeO₂, Pr₆O₁₁ and Ln₂O₃ (Ln=La, Nd, Sm) as final residues. The theoretical and experimental spectroscopic study suggests predominantly the ionic bond between the ligand and metallic center.     

New Complexes of Rare Earth Elements with 3-Methyladipic Acid

Rare earth element 3-methyladipates were prepared as crystalline solids with general formula Ln₂(C₇H₁₀O₄)₃⋅nH₂O, where n=6 for La, n=4 for Ce,Sm–Lu, n=5 for Pr, Nd and n=5.5 for Y. Their solubilities in water at 293 K were determined (2⋅10^–3–1.5⋅10^–4 mol dm^–3). The IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. During heating the hydrated 3-methyladipates lose all crystallization water molecules in one (Ce–Lu) or two steps (Y) (except of La(III) complex which undergoes tomonohydrate) and then decompose directly to oxides (Y, Ce) or with intermediate formation of oxocarbonates Ln₂O₂CO₃ (Pr–Tb) or Ln₂O(CO₃)₂ (Gd–Lu). Only La(III) complex decomposes in four steps forming additionally unstable La₂(C₇H₁₀O₄)(CO₃)₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectral and thermal studies of Y(III) and heavy lanthanide 4-chlorophthalates

Summary Complexes of heavy lanthanide(III) (Gd-Lu) and Y(III) with 4-chlorophthalic acid were prepared and their IR spectra, solubility in water at 295 K and thermal decomposition were investigated. When heated the complexes with general formula Ln₂[ClC₆H₃(CO₂)₂]₃·nH₂O where n=6 for Tb, Dy(III), n=4 for Gd, Ho and Er(III), n=2 for Tm-Lu(III) and n=3 for Y(III) decompose to the oxides Ln₂O₃, Tb₄O₇ with intermediate formation of oxochlorides LnOCl.     

Synthesis,spectroscopic and thermal studies of 2,3-naphthalenedicarboxylates of rare earth elements

The complexes of rare earth elements with 2,3-naphthalenedicarboxylic acid of the formula: Ln₂(C₁₂H₆O₄)₃·nH₂O, where Ln = La(III)-Lu(III) and Y(III); n = 3 for La(III), Ce(III); n = 6 for Pr(III)-Yb(III) and Y(III) and n = 5 for Lu(III) have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis (TG, DTG, DTA and TG-FTIR) and X-ray analysis. They are sparingly soluble in water and stable at room temperature. During heating in air atmosphere, they lose all water molecules in several steps, generally in two or three steps, except for the La(III) and Ce(III) complexes which lose all water molecules in one step. The anhydrous compounds are stable up to about 773 K and then decompose to corresponding oxides. The thermal decomposition is connected with the release of water molecules (443 K), carbon dioxide (713 K) and hydrocarbons.     

Preparation, Spectral and Thermal Studies of Y(III) and Lanthanide(III) 1-Hydroxy-2-Naphthoates

Complexes of lanthanide(III) (La–Lu) and Y(III) with 1-hydroxy-2-naphthoic acid were obtained as crystalline compounds with a general formula Ln[C₁₀H₆(OH)COO]₃⋅nH₂O:n=6 for La–Tm and Y, n=2 for Yb and n=0 for Lu. IR spectra of the prepared complexes were recorded, and their thermal decomposition in air were investigated. Spectroscopic data suggest that in the coordination of metal-organic ligand only oxygen atoms from the carboxylate group take part. When heated, the complexes decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ with intermediate formation of Ln(C₁₁H₇O₃)(C₁₁H₆O₃). This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of light lanthanide diglycolates

The conditions of thermal decomposition of La, Ce(III), Pr, Nd, Sm, Eu and Gd diglycolates have been studied. On heating, the diglycolates of Ce(III), Pr, Eu and Gd lose crystallization water and yield anhydrous salts, which are then transformed into oxides. The diglycolates of La, Nd and Sm are decomposed in three stages. First, the diglycolates undergo dehydration to form the anhydrous salts, which are next decomposed to Ln₂O₂CO₃. In the last step the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ takes place, accompanied by an endothermic effect.     

Spectral and Thermal Studies of Rare Earth Complexes With 2,4,6-trimethylbenzoic Acid

The rare earth element 2,4,6-trimethylbenzoates were prepared as solids with the general formula Ln(C₁₀ H₁₁ O₂ )₃ ×n H₂ O, where n =2 for Ln =Y, La–Nd, and n =1 for Ln =Sm–Lu. The IR spectra of the complexes prepared were recorded and their solubilities in water and thermal decomposition in the air were investigated. During heating the hydrated complexes lose all the crystallization water molecules in one (Y, Ce–Lu) or two steps (La) and then the anhydrous complexes decompose either directly to oxides (Y, Ce, Pr, Sm–Lu) or with intermediate formation oxocarbonates Ln₂ O₂ CO₃ (La, Nd). The carboxylate groups in the complexes prepared act probably as mono- and bidentate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Syntheses,characterization and thermal properties of lanthanide complexes with 2-mercaptonicotinic acid

Fourteen new complexes with the general formula of Ln(Hmna)₃·nH₂O (n=2 for Ln=La-Ho and n=1 for Er-Lu, H₂mna=2-mercaptonicotinic acid) were synthesized and characterized by elemental analyses, IR spectra and thermogravimetric analyses. In addition, molar specific heat capacities were determined by a microcalorimeter at 298.15 K. The IR spectra of the prepared complexes revealed that carboxyl groups of the ligands coordinated with Ln(III) ions in bidentate chelating mode. Hydrated complexes lost water molecules during heating in one step and then the anhydrous complexes decomposed directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The values of molar specific heat capacities for fourteen solid complexes were plotted against the atomic numbers of lanthanide, which presented as ‘tripartite effect’. It suggested a certain amount of covalent character existed in the bond of Ln³⁺ and ligands, according with nephelauxetic effect of 4f electrons of rare earth ions.     

Thermal decomposition features of calcium and rare-earth oxalates

Thermal decomposition of Ln₂(C₂O₄)₃ · 9H₂O concentrate (Ln = La, Ce, Pr, Nd) in the presence of CaC₂O₄ · H₂O was studied by X-ray diffraction, thermogravimetry, and chemical analysis. Annealing at temperatures above 374°C in the absence of calcium oxalate gives rise to the solid solution of CeO₂-based rare-earth oxides. Calcite CaCO₃ is formed in the presence of calcium oxalate at annealing temperatures above 442°C, which impedes the formation of lanthanide oxide solid solution and favors crystallization of oxides as individual La₂O₃, CeO₂, Pr₆O₁₁, and Nd₂O₃ phases. An increase in temperature above 736°C is accompanied by decomposition of calcium carbonate to give rise to an individual CaO phase and an individual phase of CeO₂-based lanthanide oxide solid solution.     

Thermal and Spectral Studies of Y(III) and Lanthanide(III) Complexes with Mesaconic Acid

Y(III) and lanthanide(III) mesaconates were prepared as crystalline solids with general formula Ln₂(C₅H₄O₄)₃⋅nH₂O, where n=7 for La−Pr, n=4 for Y,Nd−Ho, n=8 for Er−Lu. IR spectra of the prepared mesaconates suggest that carboxylate groups are bidentate bridging anf chelating. During heating the hydrated complexes are dehydrated in one (Y, Nd−Lu) or two steps (La−Pr) and then decompose directly to oxides (Y, Ce, Pr, Sm, Gd−Lu) or with intermediate formation Ln₂O₂CO₃ (La, Nd, Eu). This revised version was published online in August 2006 with corrections to the Cover Date.     

Fluorite-related phases Ln3MO7, Ln = rare earth,Y, or Sc, M = Nb,Sb, or Ta. I. Crystal chemistry

Compounds Ln₃MO₇, where Ln = La, Nd, Gd, Ho, Er, Y, or Sc, and M = Nb, Ta, or Sb have been examined by powder X-ray diffraction, electron diffraction, and electron microscopy. For large Ln cations, an orthorhombic fluorite-related superstructure is formed, of probable space group Cmcm for Ln = La and C222₁ for Ln = Nd, Gd, Ho, or Y, while for the smaller Ln cations, Er, and under some conditions, Ho and Y, the structure is defect fluorite containing microdomains of ordered, but undetermined, structure. The composition Sc₃MO₇ was not single phase under the conditions used. Compounds of the type Ln₂ScMO₇ have the pyrochlore structure.     

Thermal decomposition of rare earthp-aminosalicylates in air atmosphere

The conditions of thermal decomposition of thep-aminosalicylates of Y, La and the lanthanides from Ce(III) to Lu have been studied. On heating, the hydrated complexes of La and the light lanthanides decompose to the oxides with the intermediate formation of Ln₂[H₂N·C₆H₃(O)COO]₃. Only the complex of La decomposes to La₂O₃ through La₂[H₂N·C₆H₃(O)COO]₃ and La₂O₂CO₃. The anhydrous complexes of the heavy lanthanides decompose directly to the oxides, whereas the anhydrous complex of Y decomposes to Y₂O₃ via Y₂[H₂N·C₆H₃(O)COO]₃ formation. During heating, the hydrated complexes lose crystallization water and decompose simultaneously, and the endothermic effect of dehydration is masked by the strong exothermic effect of burning of the organic ligand.

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Zusammenfassung Es wurden die Bedingungen für die thermische Zersetzung derp-Aminosalicylate von Y, La und der Lanthanoide von Ce(III) bis Lu untersucht. Beim Erhitzen zersetzen sich die hydratierten Komplexe von La und der leichteren Lanthanoide unter Bildung des Zwischenproduktes Ln₂[H₂NC₆H₃(O)COO]₃ in ihre Oxide. Nur der Komplex mit La zersetzt sich zu La₂O₃ über die Zwischenstufen La₂[H₂NC₆H₃(O)COO]₃ und La₂O₂CO₃. Die wasserfreien Komplexe der schweren Lanthanoide zersetzen sich direkt in die Oxide, wÄhrend sich der wasserfreie Komplex von Y über die Bildung von y₂[H₂NC₆H₃(O)COO]₃ in y₂O₃ zersetzt. Beim Erhitzen verlieren die hydratierten Komplexe ihr Kristallwasser und zersetzen sich gleichzeitig, der endotherme Effekt der Dehydratation wird durch den starken exothermen Effekt der Verbrennung der organischen Liganden überdeckt.