0000000000315678
AUTHOR
M.c. Guillem
New complexes of nickel and nickel/cobalt with tetrahydrofuran-2,3,4,5-tetracarboxylic acid, THF(COOH)4. Crystal structures of Ni[THF(COOH)2(COOH)2](H2O)3 and Ni0.7Co0.3[THF(COOH)2(COO)2](H2O)3·H2O and their thermal behaviour
Abstract The reaction of NiCl2·6H2O with tetrahydrofuran-2,3,4,5-tetracarboxylic acid, THF(COOH)4, partially deprotonated by Na2CO3 (1 : 1 metal/ligand molar ratio), yielded Ni[THF(COOH)2(COO)2](H2O)3 (1). The molecular structure of 1 was determined by X-ray diffraction on the monocrystal. The structure consists of a mononuclear neutral unit with the nickel atom coordinated by a [THF(COOH)2(COO)2]2− ligand, which acts as a tridentate ligand, and three water molecules. Direct interaction of NiCl2·6H2O and CoCl2·6H2O (1 : 1 molar ratio) with THF(COOH)4 previously deprotonated by Na2CO3 (1 : 1 metal/ligand molar ratio) gave, by slow evaporation of the solution obtained, green crystals of the n…
Preparation of mixed oxides MNdO3, with M=Cr, Fe. Comparison of several methods
Abstract Different methods for the formation of NdCrO3 and NdFeO3, having the perovskite-like structure, were studied including the ceramic method, simultaneous precipitation of hydroxides and simultaneous crystallization from aqueous solutions of nitrates. Preparation of mixed oxides from hydroxides simultaneously precipitated lowered the temperature and time required for their formation. In the case of NdCrO3 the formation process from hydroxides and nitrates occurred through the chromate, NdCrO4, without intermediate decomposition of the precursor to metal oxides, which lead to the mixed oxide by 600°C.
Synthesis and structural study of sodium titanium phosphate-sodium tin phosphate solid solutions. II. Thermal expansion
Abstract The structure of NaTi 2 (PO 4 ) 3 shows the space group R3c, whereas that of NaSn 2 (PO 4 ) 3 presents the space group R3 at room temperature and it undergoes a second order phase transition at 575°C from this structure to another with the space group R3c. Evolution of the structure of NaTi 2 (PO 4 ) 3 NaSn 2 (PO 4 ) 3 solid solutions with temperature has been studied and temperature phase transition established for the compositions studied. Lattice thermal expansion of NaTi 2−x Sn x (PO 4 ) 3 solid solutions with x = 1, 1.2, 1.5 has been determined from x-ray diffraction data at temperatures ranging from 26 to 1000°C. DSC and dilatometric measurements have been also carried out o…
Structural study, thermal expansion and electrical conductivity of the composition NaSnZr(PO4)3
Abstract The structure of the composition NaSnZr(PO4)3 and its evolution with temperature has been studied. The structure presents the space group R 3 c. The refinement of the structure shows that the Sn and Zr atoms are statistically distributed over the same crystallographic position. The unit cell expands in the c direction and contracts in the a direction, remaining the space group R 3 c at temperatures between 26 and 1000°C. The low value of the electrical conductivity at 400°C, 5.729×10−7S/cm and the low density of the pellets limited the use as electrical conductor.
Synthesis and structural study of NaTi2(PO4)3-NaSn2(PO4)3 solid solutions. I. The effect of composition on lattice parameters
Abstract Compounds NaM2IV(PO4)3 with NZP-type structure present a different behavior depending on the nature of MIV. For MIV = Ti and Zr the structure shows the space group R3c, whereas for MIV = Sn the space group is R3. Differences in behavior of NaTi2(PO4)3 - NaSn2(PO4)3 solid solutions are discussed in relation to the composition. The variation of the lattice parameters with composition in NaTi2−xSnx(PO4)3 (0 1. The structure of the compound with x = 1 (NaSnTi(PO4)3) has been determined applying the Rietveld method to deconvolute the powder x-ray diffraction profile.
Preparation and structural study of sodium germanium phosphate-sodium titanium phosphate solid solutions. I. Evolution of structure with composition
Compounds NaM2IV(PO4)3 with M = Ge, Ti present the [NZP]-type structure, with a low thermal expansion. The space group at room temperature for the compound NaGe2(PO4)3 is R3, whereas for the compound NaTi2(PO4)3 is R3c. Evolution of the structure with composition in NaGe2(PO4)3 NaTi2(PO4)3 system is discussed. The space group and lattice parameters were determined for NaGe2−xTix(PO4)3 (0 < x < 2) solid solutions, prepared by ceramic method. Compositions rich in Ge(IV) (0 ≤ x ≤ 1) show the R3 space group, whereas for those rich in Ti(IV) (1.2 ≤ x ≤ 2) the space group is R3c. The variation of the lattice parameters with composition agreed with these results since it showed a change in its t…