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October 1989
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15 Reads
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3 Citations
Journal of Solid State Chemistry
Single crystals belonging to the various allotropic forms of Na3Eu(PO4)2 have been obtained by a flux method. Investigation of their structural and optical properties allows the authors to propose a model describing the successive phase transformations.
February 1986
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8 Reads
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3 Citations
Physica B+C
The magnetic properties of NaFeP//2O//7 have been experimentally studied using neutron diffraction and Moessbauer spectroscopy. The antiferromagnetic structure has been determined in space group P2//1/c prime with q equals left bracket 0, 0, 0 right bracket and mu equals 4. 53(5) mu //B. The presence of short-range ordering has been discussed on the basis of the relaxation times. A dynamical ordering process has been proposed to account for the observations over a wide range around the critical temperature.
February 1986
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42 Reads
Le Journal de Physique Colloques
The electrical conductivity of Zn1-xCoxO solid solution has been studied as a function of composition (0 ⩽ x ⩽ 0.10) and of sintering time. The behavior observed is probably due to the appearance of two energy levels in the forbidden band.
February 1986
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4 Reads
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2 Citations
Le Journal de Physique Colloques
The kinetics of reduction of zinc oxide-based varistors has been studied at 650°C in CO-CO2 mixtures in order to correlate ageing under electrical stress to diffusion phenomena. The experimental results indicate that the main cause of the ageing is a migration of oxygen from the outer core of the ZnO grains toward the intergranular phases.
January 1986
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4 Reads
A high stability vs time of the current-voltage characteristic is required for in service zinc oxide based varistors. In order to relate diffusion phenomena and aging, the kinetics of reduction of such materials in CO-CO//2 mixtures have been studied at high temperatures. The results obtained show that modification in the current-voltage characteristic accompanies oxygen transfer from the outer core of the zinc oxide grains to the intergranular phases.
July 1984
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24 Reads
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40 Citations
Journal of Solid State Chemistry
Single crystals of the high-temperature form of NaFeP2O7 have been grown by a flux technique. II-NaFeP2O7 crystallizes in the monoclinic P21/c space group with lattice parameters: a = 7.298(2) Å, b = 7.874(2) Å, c = 9.536(3) Å, beta = 111.85(2)°. The structure refined from 1481 independent reflections leads to R = 0.044 and confirms the work previously published by M. Gabelica-Robert, M. Goreaud, P. Labbe, and B. Raveau (J. Solid State Chem. 45, 389, 1982). Magnetic Mössbauer resonance studies have shown the existence of antiferromagnetic ordering with a weak ferromagnetic component below 30 K. The Fe-O bond is markedly ionic in character due to the highly polarizing power of phosphorus in tetrahedral site.
March 1983
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3 Reads
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2 Citations
Chemischer Informationsdienst
Fe2(MoO4)3 zeigt unterhalb einer Ordnungstemp. von etwa 13 K schwachen Ferrimagnetismus, der von unvollst?ndiger Kompensation der Magnetisierung der antiferromagnetisch gekoppelten Teilgitter herr?hrt.
December 1982
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9 Reads
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42 Citations
Inorganic Chemistry
Magnetic and Mössbauer resonance measurements have shown that Fe2(MoO4)3 exhibits below an ordering temperature of about 13 K a weak ferrimagnetism due to incomplete compensation of the magnetization of antiferromagnetically coupled sublattices. From the analysis of the exchange links Fe-O-Mo-O-Fe and from the Mössbauer resonance spectra a possible arrangement of the spins has been deduced.
September 1982
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7 Reads
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5 Citations
Materials Letters
The electrical properties of a phase of composition close to Zn0.99Co0.01O have been studied on pellets sintered at 1300°C under a pure oxygen stream for various periods of time. Plotting of electrical conductivity vs. temperature shows two domains characterized by two different activation energies. The high temperature activation energy depends on sintering time. The authors suggest that this property could be due to non-statistical distribution of cobalt and evaporation of zinc oxide.
December 1980
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54 Reads
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61 Citations
Journal of Solid State Chemistry
A complete and detailed structural description of sodium rare-earth orthophosphates, orthovanadates and orthoarsenates, with general formula Na3Ln(XO4)2 (Ln = rare-earth, X = P, V, As), is presented. Their structural evolution has been studied not only as a function of the Ln3+ ion size and the (XO4)3− group, but also as a function of temperature. A number of allotropic forms have been observed for each pair Ln3+−(XO4)3−. The different structure types found during this study have been identified due to the complete structure determinations of the low temperature varieties of Na3Nd(PO4)2, Na3La(VO4)2, Na3Nd(VO4)2 and Na3Er(VO4)2, and the high temperature form of Na3Yb(PO4)2. The first four structures can be considered as derivated structures of the glaserite type, while the last one corresponds to phases having an extended non-stoichiometry and is related to the structure of NaZr2(PO4)3.
... (b). All samples showed a doublet with isomer shift (δ) near to 0.41 mm/s, related to paramagnetic Fe 3+ ion in high spin state and quadrupole splitting (Δ) at 0.18 mm/s, which is assigned to [FeO 6 ] sites in Fe 2 Mo 3 O 12 monoclinic phase[42]. Spectra of sintered samples showed a low intensity simple sextet, indicating a magnetically ordered state. The high value of hyperfine field (above 51 T), and the values of δ near 0.37 mm/s indicates the presence of α-Fe 2 O 3 ...
March 1983
Chemischer Informationsdienst
... The compounds in the ordered aeschynite family RMWO 6 (R = rare-earth, M = Fe, Cr, and V) [17,22,23,[26][27][28][29][30][31][32] crystallize in an orthorhombic structure with the polar space group Pna2 1 , where the transition metal ions M 3+ and W 6+ form an ordered arrangement. These compounds can be considered an ordered derivative of the centrosymmetric (Pnma) parent compound CaTa 2 O 6 [33]. ...
January 1974
... The data suggest that the structure of La2PdO 4 is of Nd2CuO4-type, rather than the K2NiF4-type, as the c/a ratio is characteristic of the former structure, but too small to be consistent with the latter. A large number of phases of the system Ln,AM, O3,+l (Ln = rare earth ion, A = alkaline earth ion and M = Co, Ni, Cr, AI, Fe, Mn, Ru, Rh, Ga) have been reported in the literature (Blasse 1965Blasse , 1968 Joubert et al 1970; Fava et al 1972; Daoudi and Flem 1973; Samaras et al 1973; Demazeau et al 1976a Demazeau et al , b, 1979 Benabad et al 1977; Cheruy and Joubert 1981; Singh 1995b, 1997 ). Most of these compounds, showing interesting electric transport and magnetic properties, crystallize either in the tetragonal or orthorhombic crystal symmetry in the space group 14/mmm, Fmmm or Cmca. ...
October 1977
Journal of Solid State Chemistry
... The unit-cell parameters of dobrovolskyite (dob) and aphthitalite (apth) are related by the ratios: a dob ≈ 3a apth , c dob ≈ 3c apth , whereas the unit-cell parameters of dobrovolskyite and NASICON-like (nas) phases are related by the ratios: a dob ≈ 2a nas , c dob ≈ 3c nas . The relationships between the unit-cell parameters and the crystal structures of aphthitalite and NASICON-like compounds were discussed by Vlasse et al. (1980), who concluded that both families contain similar fundamental building blocks. Kostov-Kytin et al. (2013) investigated phase transformations of the aphthitalite-like zirconosilicate Na 3 HZrSi 2 O 8 ⋅0.4H 2 O and reported the existence of a structural phase transition from the aphthitalite to the NASICON structure types at 700°C. ...
December 1980
Journal of Solid State Chemistry
... [1][2][3] The double molybdates and tungstates ALn(MO 4 ) 2 with M = Mo, W, [4][5][6][7] or the orthophosphates A 3 Ln(PO 4 ) 2 , where A is a univalent cation and Ln is a lanthanide, were found to exhibit excellent PL properties. [8][9][10] Mixed host lattices containing two different tetrahedral units in the lattice, such as the molybdeno or tungsto/phosphates K 2 Bi(MoO 4 )(PO 4 ):Eu 3+11 and the vanadophosphates K 3 Ln 1-x Eu x (VO 4 ) 2-x (PO 4 ) x with Ln = Sc, Y, Gd, La 12,13 were also proved to be promising phosphors for SSL applications. ...
August 1980
Solid State Communications
... The growing interest in using rare earth doped materials as optical temperature sensors particularly the Er 3+ ion is primarily owing to their high electrical passiveness, negligible electromagnetic interference, ample dynamic range, and multifold competence [42][43][44]. The Er 3+ ion has two thermally coupled energy levels, 2 H 11/2 and 4 S 3/2 , with a little energy J o u r n a l P r e -p r o o f difference of approximately 770 cm -1 , which is of the same order of scale as that of the thermal energy K B T (～210 cm -1 ) at ambient temperature. ...
May 1978
Materials Research Bulletin
... Geometrically frustrated magnets provide an intriguing playground for investigation of the novel phenomena in condensed matter physics [1][2][3]. Strong frustrations may produce large degeneracy of the ground state and prevent formation of magnetic order in favor of exotic states such as quantum spin-liquid (QSL) or spin-ice phases [2][3][4]. ...
January 1979
Materials Research Bulletin
... The main crystallization product of PFN2 is NaFeP 2 O 7 . In this phase, these are P 2 O 7 dimers connected to each other by Fe 3+ octahedrons [42]. The monoclinic FePO 4 is built of separated [PO 4 ] tetrahedra connected to each other by Fe of 5 coordination to oxygen. ...
July 1984
Journal of Solid State Chemistry
... Since we are focused on FM/AFM interfaces and EB effect, we have designed two quasi-2D layered compounds by introducing Mn ions in the perovskite layer of SrLaFe 0.5 Co 0.5 O 4 , in order to enhance the FM contribution and magnetic inhomogeneity. Thus, the present work gives a comparative study on the impact of Mn ions on the structural and magnetic features of Co-rich compound SrLaFe 0. 25 [20] and the crystallographic structure was constructed using VESTA [21]. X-ray photoelectron spectroscopy (XPS) was performed using Nexsa x-ray photoelectron spectrometer system by ThermoFisher Scientific. ...
October 1977
Journal of Solid State Chemistry
... As far as we know, the compounds with general chemical formula Na 3 M(VO 4 ) 2 had diversified crystal structure [19,[22][23][24][25], such as Na 3 Gd(VO 4 ) 2 for monoclinic system (Space group:P21/c), Na 3 Er(VO 4 ) 2 for monoclinic system (Space group:P21/n), Na 3 La(VO 4 ) 2 for orthorhombic system (Space group:Pbc21). In this study, fully concentrated Eu 3+ -based Na 3 Eu(VO 4 ) 2 vanadate phosphor was synthesized. ...
October 1976
