| 1. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Synthesis and structural characterization of perovskite type proton conducting BaZr1-xInxO3-delta (0.0 <= x <= 0.75)
- 2006
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 177:17-18, s. 1395-1403
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Tidskriftsartikel (refereegranskat)abstract
- Solid state sintering has been used to prepare the cubic perovskite structured compounds BaZr1-xInxO3-delta (0.0 <= x <= 0.75). Analysis of X-ray powder diffraction (XRPD) data reveals that the unit cell parameter, a, increases linearly with an increased Indium concentration. XRPD data was also used to demonstrate the completion of sample hydration, which was reached when the materials showed a set of single-phase Bragg-peaks. Dynamic thermogravimetric analysis (TGA) data showed that approx. 89% of the total number of available oxygen vacancies can be filled in BaZr1-xInxO3-delta for x=0.50, and that the maximum water uptake occurs below 300 degrees C. Rietveld analysis of the room temperature neutron powder diffraction (NPD) data confirmed the average cubic symmetry (space group Pm-3m), and an expansion of the unit cell parameter after the hydration reaction. The strong O-H stretch band, 2500-3500 cm(-1), in the infrared absorbance spectrum clearly manifests the presence of protons in the hydrated material. Proton conductivity of hydrated BaZr1-xInxO3-delta, x=0.75 was investigated during heating and cooling cycles under dry argon atmosphere. The total conductivity during the heating cycle was nearly two orders of magnitude greater than that of cooling cycle at 300 degrees C, whilst these values were similar at higher temperatures i.e. T > 600 degrees C.
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| 4. |
- Azad, AK, et al.
(författare)
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Nuclear and magnetic structure of Ca2MnWO6: A neutron powder diffraction study
- 2001
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Ingår i: MATERIALS RESEARCH BULLETIN. - 0025-5408. ; 36:13-14, s. 2485-2496
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Tidskriftsartikel (refereegranskat)abstract
- The nuclear and magnetic structures of the double provskite compound Ca2MnWO6 have been determined by neutron powder diffraction. Rietveld refinement shows that the compound adopts a monoclinic crystal structure with P2(1)/n symmetry. Magnetic refinement
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| 5. |
- Azad, AK, et al.
(författare)
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Preparation, Crystal and Magnetic Structure of the Double Perovskite Ba2FeWO6
- 2002
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. ; A 74, s. S763-765
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Tidskriftsartikel (refereegranskat)abstract
- Single-phase polycrystalline material of the double perovskite Ba2FeWO6 was prepared and characterized by X-ray and neutron powder diffraction (NPD). The crystal structure was tetragonal with lattice parameters a=b=5.7479(4) Å and c=8.1444(9) Å at room temperature (295 K). NPD data at 10 K shows the evidence of an antiferromagnetic ordering of the Fe atoms. The reverse Monte Carlo powder (RMCPOW) technique was used to find the magnetic structure, which showed that it is based on a unit cell related to that of the nuclear structure by the propagation vector 0 \frac[¯]1[¯][¯]2[¯] \frac[¯]1[¯][¯]2[¯] . An ordering of collinear spins was found with alternate layers in the c-direction or in the a-b plane. The model was checked by Rietveld refinement and the magnetic moment of iron was found to be 3.39(2)7B at 10 K.
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| 8. |
- Azad, AK, et al.
(författare)
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Synthesis, crystal structure, and magnetic characterization of the double perovskite Ba2MnWO6
- 2001
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Ingår i: MATERIALS RESEARCH BULLETIN. - 0025-5408. ; 36:12, s. 2215-2228
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Tidskriftsartikel (refereegranskat)abstract
- The double perovskite Ba2MnWO6 has been prepared as a pure powder by a conventional solid-state reaction process and studied by X-ray, neutron powder diffraction (NPD), magnetization, and AC susceptibility measurements. NPD, magnetization, and AC suscepti
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| 9. |
- Baron, V, et al.
(författare)
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Neutron powder diffraction study of Mn-bearing hematite, α-Fe2−xMnxO3, in the range 0 x 0.176
- 2005
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Ingår i: Solid State Sciences. - : Elsevier BV. - 1293-2558. ; 7:6, s. 753-759
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Tidskriftsartikel (refereegranskat)abstract
- A detailed neutron powder diffraction and calorimetric study was conducted to determine the influence of increasing Mn-substitution on the crystal and the magnetic structures of hematite, α-Fe2O3. The study was initiated to determine, if Mn substitution may be responsible for unusual ferromagnetic properties of natural hematite samples from the Kalahari Mn field, South Africa. Natural as well as synthetic Mn-bearing hematite samples with the compositional range Fe2−xMnxO3 (x=0 to 0.176) were examined. Calorimetric measurements were performed to determine the Néel TN and the Morin TM temperature transitions. All studied hematite samples, irrespective of chemical composition, display weak ferromagnetism at 295 K and coexistence of weak ferromagnetic and antiferromagnetic phases at 10 K. A slight decrease of the total magnetic moment and TM but a drastic decrease of TN can be attributed to increasing Mn-substitution. The results illustrate that Mn substitution may contribute but cannot be the sole reason for the unusual magnetic properties of natural hematite samples.
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| 10. |
- Bashir, J., et al.
(författare)
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The influence of Cr doping on the structural and magnetic properties of Sr2Fe1-xCrxMoO6 double perovskite
- 2006
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 385, s. 126-129
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effect of Cr substitution for Fe in Sr2Fe1-xCr,MoO6 (x <= 0.3) double perovskites. X-ray diffraction, neutron powder diffraction (NPD), magnetisation measurements as well as Mossbauer spectroscopy have been used to determine the structural and magnetic properties of these compounds. All these materials were found to crystallise with tetragonal symmetry. The main observed effect is a decrease with respect to the undoped composition, of the cationic order with Cr doping levels. Mossbauer spectroscopy measurement revealed that iron exists in high spin + 3 oxidation state.
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