Browsing by Author "Ting, J"
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- ItemAntiferromagnetism in a technetium oxide. Structure of CaTcO3(American Chemical Society, 2011-01-16) Avdeev, M; Thorogood, GJ; Carter, ML; Kennedy, BJ; Ting, J; Singh, DJ; Wallwork, KSThe technetium perovskite CaTcO3 has been synthesized. Combining synchrotron X-ray and neutron diffraction, we found that CaTcO3 is an antiferromagnetic with a surprisingly high Neel temperature of ~800 K. The transition to the magnetic state does not involve a structural change, but there is obvious magnetostriction. Electronic structure calculations confirm the experimental results. © 2011, American Chemical Society
- ItemChemInform abstract: synthesis and structural studies of lanthanide substituted bismuth—titanium pyrochlores(Wiley, 2009-06-12) Ting, J; Kennedy, BJ; Withers, RL; Avdeev, MBi2/3Ln4/3Ti2O7 (Ln: La, Nd, Eu, Ho, Yb) pyrochlores are synthesized by solid state reaction of stoichiometric mixtures of Bi2O3, TiO2, and Ln2O3 (900, 1000, and 1100 °C, 48 h each) and characterized by powder XRD. The presence of six-fold disorder, associated with the Bi 6s2 lone pair electrons, is believed to stabilize the unexpected stoichiometry. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemCrystal structures and phase transitions in a-site deficient perovskites Ln1/3TaO3(American Chemical Society, 2008-11-11) Zhou, QD; Saines, PJ; Sharma, N; Ting, J; Kennedy, BJ; Zhang, Z; Withers, RL; Wallwork, KSThe synthesis and structures of the perovskites Ln1/3TaO3 are described. As the size of the Ln cation is reduced, the compounds display a sequence of structure: P4/mmm/La → Cmmm/Ce−Gd → Pmma/Tb, Dy → Pmc21/Ho, Er. Although apparently tetragonal in P4/mmm, electron diffraction patterns of Tm1/3TaO3 reveal this has a complex incommensurate structure. Likewise Gd1/3TaO3 appears metrically tetragonal, but electron diffraction and synchrotron X-ray powder diffraction demonstrate this is actually orthorhombic. The suppression of the spontaneous orthorhombic strain in Gd1/3TaO3 is thought to be due to the proximity to the first-order Cmmm−Pmma transition. Variable temperature studies show both Tb1/3TaO3 and Dy1/3TaO3 undergo a first-order Cmmm−Pmma transition upon heating. © 2008, American Chemical Society
- ItemOxygen deficient lead-technetium pyrochlore, the first example of a stable valence V technetium oxide?(European Association of Geochemistry and the Geochemical Society (Goldschmidt), 2021-07-05) Thorogood, GJ; Avdeev, M; Carter, ML; Losurdo, L; Saura-Múzquiz, M; Thorogood, KJ; Ting, J; Wallwork, KS; Zhang, Z; Kennedy, BJDespite the fact that Technetium V oxides are possible there are very few reports of their existence. Most recently Lawler et.al. [1] have reported the structure of Tc2O5 “tech red” and have noted that it is indeed volatile. It is apparent from this study that there is no stable form and they draw parallels with a well-studied analogue of Tc2O5, Re2O5 that disprortioniates into Re(4+) and Re(7+) species. Given these parallels we investigated PbTcO3 as reported by Muller et.al [2] to be a pyrochlore in an attempt to determine if there were parallels with Pb2Re2O7-d. The structure of lead-technetium pyrochlore has been refined in space group with a = 10.36584(2) Å using a combination of synchrotron X-ray and neutron powder diffraction data and confirmed via Electron Diffraction. The oxide is found to be oxygen deficient with a stoichiometry of Pb2Tc2O6.86. The displacive disorder of the Pb cations is evident from the refinements as has been observed Bi2Tc2O7-d. X-ray absorption measurements at the Tc K-edge demonstrate the valence of the Tc is greater than 4.0 as anticipated from the refined oxygen stoichiometry. Raman spectroscopy confirms the local coordination of the Technetium leading us to conclude that this pyrochlore is the first example of a stable valence V Technetium oxide. [1] Lawler, K. V. et al. Unraveling the mystery of ‘tech red’-a volatile technetium oxide. Chem. Commun. 54, 1261–1264 (2018). [2] Muller, O., White, W. B. & Roy, R. Crystal chemistry of some technetium-containing oxides. J. Inorg. Nucl. Chem. 26, 2075–2086 (1964).
- ItemStructural characterisation of the perovskite series Sr0.9-xCaxCe0.1MnO3: influence of the Jahn-Teller effect(Elsevier, 2009-04) Kennedy, BJ; Ting, J; Zhou, QD; Zhang, Z; Matsuda, M; Miyake, MFifteen perovskite-type compounds Sr0.9−xCaxCe0.1MnO3, x=0–0.9 in steps as fine as 0.05, have been synthesised by solid state methods, and the room temperature structures characterised using X-ray synchrotron powder diffraction. At low Ca contents (x≤0.45) the structures are tetragonal in space group I4/mcm and at high Ca contents (x≥0.55) the compounds are orthorhombic in space group Pbnm. At room temperature these two phases co-exist in the compound with x=0.5. XANES measurements show the Ce to be present as Ce4+ in all the oxides. High temperature structures are reported for selected members. © 2009, Elsevier Ltd.
- ItemStructural phase transitions and magnetic order in SrTcO3(Royal Society of Chemistry, 2011-07-21) Thorogood, GJ; Avdeev, M; Carter, ML; Kennedy, BJ; Ting, J; Wallwork, KSThe structure of the perovskite SrTcO3 has been investigated using both synchrotron X-ray and neutron powder diffraction. At room temperature SrTcO3 is orthorhombic as a consequence of cooperative tilting of the corner sharing TcO6 octahedra. The tilts are sequentially removed as the sample is heated with the oxide displaying the sequence of structres Pnma [rightward arrow] Imma [rightward arrow] I4/mcm [rightward arrow] Pm3[3 with combining macron]m. Neutron powder diffraction data collected in the temperature range 4-1023 K indicate that SrTcO3 has G-type antiferromagnetic structure, in which each Tc moment is antiparallel to its six nearest neighbours, below [similar]1000 K. The magnetic structure is collinear antiferromagnetic with the technetium moments parallel to c-axis and can be described by the propagation vector k = [0,0,0] and the basis vector (0,0,Az). The same magnetic structure is observed in each of the four crystal structures.© 2011, Royal Society of Chemistry
- ItemStructural studies of SrTcO3, CaTcO3, and Pb2Tc2O7-d(International Union of Crystallography, 2011-08-22) Thorogood, GJ; Kennedy, BJ; Avdeev, M; Ting, J; Zhang, Z; Carter, MLLittle is known regarding the structure and properties of technetium oxides. This is mainly due to the absence of any naturally occurring Tc isotopes and the radioactivity of those available [1]. Tc oxides are important since 99Tc is found in nuclear waste and has a long half-life (2.13 × 105 yr). Tc is a 4d element, and like its lighter analogue Mn a 3d element it can adopt a number of oxidation states. 3d oxides are generally, but not always magnetic, while 4d and 5d oxides, with their more spatially extended d-orbitals tend not to be magnetic although SrRuO3 [2] is a notable exception. Here we have combined synchrotron X-ray and neutron diffraction to examine the structure of CaTcO3, SrTcO3 and Pb2Tc2O7-d. The only previous report on these materials was by Muller, White and Roy in 1964 [3]. They reported the existence of these materials and suggested the CaTcO3 and SrTcO3 were orthorhombic whereas the Pb2Tc2O7-d was reported as being pyrochlore. This earlier work concentrated on syn-thesis hence little is known about these three compounds and there has been no study of their structures or magnetic properties. © International Union of Crystallography
- ItemStructure and cation ordering in spinel-type TcCo2O4. An example of a trivalent technetium oxide(Royal Society of Chemistry, 2011-11-11) Thorogood, GJ; Zhang, Z; Hester, JR; Kennedy, BJ; Ting, J; Glover, CJ; Johannessen, BThe structure of TcCo(2)O(4) has been determined using a combination of synchrotron X-ray and neutron powder diffraction methods. It has an inverse spinel structure where the Tc occupies the octahedral sites. Both the refined Tc-O distance and X-ray absorption spectra suggest the Tc is predominantly trivalent. The structure of TcCo(2)O(4) has been determined using a combination of synchrotron X-ray and neutron powder diffraction methods. It has an inverse spinel structure where the Tc occupies the octahedral sites. Both the refined Tc-O distance and X-ray absorption spectra suggest the Tc is predominantly trivalent.© 2011, Royal Society of Chemistry
- ItemStructure and properties of manganese-substituted bismuth titanates(IOP Publishing, 2010-10-01) Ting, J; Kennedy, BJPartial substitution of manganese for titanium in bismuth titanate is a potential method to introduce ferromagnetic properties to ferroelectric bismuth titanate. We have established that manganese-substituted bismuth titanate forms only at low manganese contents. As the manganese content is increased, secondary phases form. A combination of neutron and synchrotron X-ray powder diffraction has been used to determine the structure of manganese-substituted bismuth titanates with chemical composition Bi 4 Mn x Ti 3_x O 12 (0 ≤ x ≤1 at 0.05 steps). Measurements between 4 K and 1073 K have been used to examine the phase transitions that they undergo. It was found the substitution of manganese into bismuth titanate increases the phase transition temperature to tetragonal by about 100 °C. Neutron diffraction and bulk magnetic susceptibility measurements demonstrate the absence of long-range magnetic cation ordering in selected examples. (c) 2011 IOP Publishing LTD
- ItemStructure and properties of new technetium compounds(Australian Institute of Physics, 2013-02-06) Thorogood, GJ; Kennedy, BJ; Avdeev, M; Ting, J; Zhang, ZM; Lumpkin, GRNot available
- ItemSynthesis and structural studies of lanthanide substituted bismuth-titanium pyrochlores(Elsevier, 2009-04) Ting, J; Kennedy, BJ; Withers, RL; Avdeev, MThe identity of the pyrochlore phase seen during the synthesis of ferroelectric Bi(4-x)Ln(x)Ti(3)O(12) Aurivillius oxides is shown to be Bi(2/3)Ln(4/3)Ti(2)O(7). This pyrochlore is only stable for Ln(3+) = Sm3+ or smaller. For larger lanthanides the layered Aurivillius oxide is favoured. The presence of six-fold disorder, associated with the Bi 6s(2) lone pair electrons, is believed to stabilise the unexpected stoichiometry of this oxide. Precise structures, obtained by Rietveld refinement from synchrotron X-ray diffraction data, of three examples Ln(3+) = Eu, Ho and Yb are presented. © 2009, Elsevier Ltd.
- ItemSynthesis and structural studies of the transition-metal-doped Rh perovskites LaMn0.5Rh0.5O3 and LaCu0.5Rh0.5O3(American Chemical Society, 2010-03-09) Ting, J; Kennedy, BJ; Zhang, Z; Avdeev, M; Johannessen, B; Jang, LYThe two orthorhombic perovskites LaMn0.5Rh0.5O3 and LaCu0.5Rh0.5O3 have been characterized using X-ray absorption near edge structure (XANES) measurements and powder synchrotron X-ray and neutron diffraction. The Mn and Rh in LaMn0.5Rh0.5O3 are essentially trivalent and disordered onto the same crystallographic site. The absence of an appreciable Jahn−Teller (JT) distortion of the BO6 octahedra is a consequence of this disorder and large magnitude of the octahedral tilting. XANES measurements show that the Rh in LaCu0.5Rh0.5O3 has a valence state of around +3.5 as a consequence of extensive charge delocalization between the Cu and Rh cations, that are also disordered onto a single site. These two effects combine to further reduce the distortion of the octahedra in LaCu0.5Rh0.5O3 relative to that of LaMn0.5Rh0.5O3. © 2010, American Chemical Society
- ItemSynthesis and structure of oxygen deficient lead-technetium pyrochlore, the first example of a valence V technetium oxide(Frontiers Media, 2021-07-01) Kennedy, BJ; Ablott, TA; Avdeev, M; Carter, ML; Losurdo, L; Saura-Múzquiz, M; Thorogood, KJ; Ting, J; Wallwork, KS; Zhang, ZM; Zhu, HL; Thorogood, GJThe structure of lead-technetium pyrochlore has been refined in space group F d 3 ¯ m with a = 10.36584(2) Å using a combination of synchrotron X-ray and neutron powder diffraction data and confirmed via Electron Diffraction. The oxide is found to be oxygen deficient with a stoichiometry of Pb2Tc2O7-d. Displacive disorder of the Pb cations is evident from the refinements, as has been observed in Bi2Tc2O7-d. X-ray absorption spectroscopic measurements at the Tc K-edge demonstrate the valence of the Tc is greater than 4.0 as anticipated from the refined oxygen stoichiometry. Raman spectroscopy confirms the presence of disorder leading us to conclude that this pyrochlore is the first example of a valence V technetium oxide. © 2021 Kennedy, Ablott, Avdeev, Carter, Losurdo, Saura-Muzquiz, Thorogood, Ting, Wallwork, Zhang, Zhu and Thorogood. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).