Sodium rare earth metal amides Na3 RE(NH2)6 (RE = La–Nd, Er, Yb) from ammonothermal synthesis

The amides Na3 RE(NH2)6 have been obtained from the metals in supercritical ammonia under ammonobasic conditions at 573 K and 70 MPa for RE = La–Nd, and at 473 K and 40 MPa for RE = Er, Yb. All compounds are formed in the hot zone within a temperature gradient, indicating a retrograde solubility under the applied process conditions. These amides represent soluble intermediates in ammonothermal binary rare earth metal nitride synthesis. All compounds were obtained as microcrystalline powders, while single crystals of those amides containing the heavier rare earth metals could be isolated. The crystal structures were solved and refined from single-crystal and powder X-ray diffraction intensity data. The results of vibrational spectroscopy are reported. Thermal analysis measurements under inert gas atmosphere demonstrated a decomposition to the respective black binary rare earth metal nitrides REN1−δ .

Effect of binary rare earth oxide on the properties of plasma sprayed Al2O3/TiO2 coatings

Purpose This study systematically investigated the effect of the binary rare earth oxide of La2O3 and Sm2O3 on the properties of the Al2O3/TiO2 (AT) coating, including phase transform, wear behavior, etc. Design/methodology/approach AT coatings mixed with different components of binary rare earth oxides of La2O3 and Sm2O3 are prepared by atmospheric plasma spraying. The adhesion strength, micro-hardness, phase transition and tribological behavior of coatings are systematically investigated. Findings The X-ray diffraction (XRD) analysis shows that phase transformation is obvious after spraying, and a-Al2O3 is almost translated into γ-Al2O3 when La2O3 and Sm2O3 are doped together. Meanwhile, solid solution generated between rare earth oxide and Al2O3/TiO2 coatings results in disappearance of TiO2 and rare earth oxide phase. The photos under the scanning electron microscope (SEM) indicate that binary rare earth oxide could increase the melting degree of powder and decrease porosity of coatings.The increasing of Sm2O3 rarely affect micro-hardness and adhesion strength, and the coating with 4 per cent Sm2O3 and 1 per cent La2O3 exhibits the best wear resistance and lowest friction coefficient among all the samples. Originality/value AT coatings mixed with different components of binary rare earth oxide of La2O3 and Sm2O3 are prepared by atmospheric plasma spraying. Binary rare earth oxide could increase the melting degree of powder and decrease porosity of AT coatings.

AB INITIO STUDY OF ELECTRONIC AND MAGNETIC STRUCTURE OF INTERMETALLIC RE5Ge3 COMPOUNDS

A series of binary rare-earth metal germanides RE 5 Ge 3 ( RE = La , Ce , Pr and Nd ) adopting the Mn 5 Si 3-type hexagonal structure is studied. These intermetallic phases show a complex magnetic behavior. Using a modification of the local density approximation (LSDA + U) the magnetic and electronic properties of these compounds are calculated. The spin-orbit coupling (SOC) was included using a full relativistic basis. Besides the structural parameters, bonding characters, total and partial densities of state and band structures are analyzed and compared with the experimental findings.