Browsing by Author "Short, SM"

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    Incomplete and irreversible high-pressure induced ferroelectric to antiferroelectric phase transition of PZT95/5(2Nb) studied by in-situ neutron diffraction
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Avdeev, M; Jorgensen, JD; Short, SM; Morosin, B; Venturini, EL; Yang, P; Samara, GA
    Zr-rich lead zirconate titanate ceramic and powder samples with composition near Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 [PZT95/5(2Nb)] have been studied in the range of hydrostatic pressure (0—6.2 kbar) and temperature (10 295 K) by time-of-flight neutron powder diffraction and dielectric measurements. The transformation from the ferroelectric R30 phase FR(LT) to the antiferroelectric Pbam phase is incomplete: even at our highest pressure of 6.2 kbar, §wt.% of the sample remains in the FR(LT) phase. On pressure release to i bar at 295 K, only 26% of the FR(LT) phase is recovered. © The Authors
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    Structural, magnetic and electronic properties of LaNi0.5Fe0.5O3 in the temperature range 5-1000 K
    (Elsevier, 2008-08) Gateshki, M; Suescun, L; Kolesnik, S; Świerczek, K; Short, SM; Dabrowski, B; Mais, J
    The structure, magnetism, transport and thermal expansion of the perovskite oxide LaNi0.5Fe0.5O3 were studied over a wide range of temperatures. Neutron time-of-flight data have shown that this compound undergoes a first-order phase transition between similar to 275 and similar to 310K. The structure transforms from orthorhombic (Pbnm) at low temperatures to rhombohedral (R (3) over barc) above room temperature. This phase transition is the cause for the previously observed co-existence of phases at room temperature. The main structural modification associated with the phase transition is the change of tilting pattern of the octahedra from a(+)b(-)b(-) at low temperatures to a(-)a(-)a(-) at higher. Magnetic data strongly suggests that a spin-glass magnetic state exists in the sample below 83 K consistent with the absence of magnetic ordering peaks in the neutron data collected at 30K. At high temperatures the sample behaves as a small polaron electronic conductor with two regions of slightly different activation energies of 0.07 and 0.05 eV above and below 553 K, respectively. The dilatometric data show an average thermal expansion coefficient of 14.7 x 10(-6) K-1 which makes this material compatible with frequently used electrolytes in solid oxide fuel cells. © 2008, Elsevier Ltd.