[en] The ternary borate systems Na₂O-Ln₂O₃-B₂O₃ (Ln = La, Nd) have been investigated in view of obtaining high-neodymium-concentration materials with weak concentration quenching. A ternary phase of composition Na₃Ln(BO₃)₂ (Ln = La, Nd) has been found. It crystallizes in the monoclinic space group P2₁/c. The structure has been determined for Na₃Nd(BO₃)₂. A full-matrix least-squares refinement led to R = 0.040. The structure is formed by isolated BO₃ triangles held together by the neodymium and sodium ions. The rare-earth atoms have a complex eightfold coordination in a covalent BO₃ matrix

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[en] The structure of the ternary boride Nd/sub 0.71/Rh/sub 3.29/B₂ was determined by single-crystal X-ray diffraction. It has a hexagonal symmetry with space group P62m and cell parameters a = 5.595(2) and c = 2.855(1) angstrom. Its structure is similar to that of the other CeCo₃B₂-type ternary borides. It is made up of two types of alternating layers, parallel to the (001) plane, formed by either (Nd,Rh) and B atoms or by Rh atoms alone

[en] The use of europium as a local structure probe allowed the authors to determine the various phases appearing at room temperature in the NaPO₄-Na₃Eu(PO₄)₂ and NaSrPO₄-Na₃Eu(PO₄)₂ systems. The broadening of the europium emission lines in going from the calcium to the strontium phases illustrates the ease of movement of the [PO₄] groups

[en] The reaction of rare-earth nitrides with fluorides or the pyrolysis of these fluorides in gaseous ammonia atmosphere leads, in the case of lanthanum, cerium, and gadolinium, to nitride fluorides of general formula LnN/sub x/F/sub 3-3x/. They crystallize with a fluorite-type structure which can be described in a consistent manner in terms of a Willis model. The magnetic properties of Gd₃NF₆ have been studied

[en] New ternary silicides LaRhSi, LaIrSi and NdIrSi have been synthesized by arc melting. On the basis of the ZrOS structure, their powder patterns have been indexed using a primitive cubic unit cell with space group P2₁3. LaRhSi and LaIrSi have a superconducting transition at 4.35K and 2.3K respectively. NdIrSi shows spontaneous magnetization below Tsub(C) = 10K and its magnetic structure is probably non colinear. (author)

[en] Phases related to the different forms of K²SO⁴ have been studied in the Na³PO⁴-Sr³(PO⁴)²-EuPO⁴ system by DTA and X-ray diffraction. They appear within the range of composition limited by the solid solutions NaSr_1-xEu_2x3/vacant_x4/PO⁴ and Na_2+ySr_2(1-y)Eu_y(PO⁴)². At high temperature the α-K²SO⁴ structure type seems to be adopted, while at low temperature the various phases crystallize with structures related to the ß-K²SO⁴ type. (author)

[en] New ternary silicides RE₂Rh₃Si₅ (RE = Y, La, Nd, Sm, Gd, Tb, Dy, Ho, Er) have been prepared. They crystalize in the U₂Co₃Si₅-type structure. Only the silicides containing the diamagnetic rare earths Y and La show a superconducting transition at T /SUB cr/ = 4.4 + or - 0.2K and T /SUB cr/ = 2.7 + or - 0.1K respectively, those with magnetic rare earths order antiferromagnetically at low temperature

[en] The use of europium as a local structural probe allows the various phases appearing in the NaCaPO₄-Na₃Eu(PO₄)₂ and NaSrPO₄-Na₃Eu(PO₄)₂ systems to be detected. The broadening of the europium emission lines in going from the calcium to the strontium phases illustrates the ease of displacement of the PO₄ groups. (Auth.)

[en] Containerless processing of YBa₂Cu₃O_7-δ was performed using drop tube and aero-acoustic levitation techniques. In drop tube experiments, two solidification microstructures developed which corresponded to the degree of melting. In aero-acoustic levitation experiments, three solidification microstructures developed. One microstructure was the result of incomplete homogenization of the melt. The second was due to slight undercooling into the Y₂O₃ + liquid region of the phase diagram upon which primary Y₂O₃ dendrites formed. The third was due to much deeper undercooling. In this case, the primary solidification structure consisted of dendrites of tetragonal 1:2:3 and some other interdendritic phase. Subsequent to solidification processing, these samples were annealed to single phase 1:2:3 with orthorhombic symmetry. SQUID magnetometer measurements indicated a sharp superconducting transition at approximately 85 K. Magnetic J_c values, calculated using the Bean critical state model, indicated that the deeply undercooled and annealed samples had critical current densities on the order of 10⁴ Acm^-2