Browsing by Author "Scott, J. F."

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    Giant electrocaloric effect in the thin film relaxor ferroelectric 0.9 PbMg1/3Nb2/3O3–0.1 PbTiO3 near room temperature.
    (American Institute of Physics, 2006-12) Mischenkoa, A. S.; Zhang, Qi; Whatmore, Roger W.; Scott, J. F.; Mathurb, N. D.
    We have recently observed a giant electrocaloric effect (12 K in 25 V) in 350 nm sol-gel PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of 242oC. Here we demonstrate a giant electrocaloric effect (5 K in 25 V) in 260 nm sol-gel films of the relaxor ferroelectric 0.9 PbMg1/3Nb2/3O3 – 0.1 PbTiO3 near the Curie temperature of 60oC. This reduction in operating temperature widens the potential for applications in novel cooling systems.
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    Investigation of the electrocaloric effect in a PbMg2/3Nb1/3O3-PbTiO3 relaxor thin film
    (American Institute of Physics, 2009-05) Correia, T. M.; Young, J. S.; Whatmore, Roger W.; Scott, J. F.; Mathur, N. D.; Zhang, Qi
    Permittivity measurements of a 0.93PMN-0.07PT thin film show a broad maximum near 35 °C, and an anomaly at the depolarizing temperature Td = 18 °C on heating only, suggesting a dipolar glass-relaxor phase transition. No structural phase transition at 18 °C is apparent from ferroelectric hysteresis loops taken on field cooling and field heating. These loops show the thermal hysteresis expected for ferroelectric relaxors, which has not hitherto been experimentally verified in PbMg2/3Nb1/3O3-PbTiO3 thin films. Our data suggest the intriguing possibility of a giant electrocaloric effect (ΔT = 9 K, ΔE = 720 kV cm−1) at and near room temperature.
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    PST thin films for electrocaloric coolers
    (Iop Publishing Ltd, 2011-04-07T00:00:00Z) Correia, T. M.; Kar-Narayan, S.; Young, J. S.; Scott, J. F.; Mathur, N. D.; Whatmore, Roger W.; Zhang, Qi
    Relaxor behaviour in a thin film of partially ordered PbSc0.5Ta0.5O3 (PST) was confirmed via slim P-E loops and the frequency dependence of the temperature at which the dielectric constant is maximum. Indirect measurements of the electrocaloric effect suggest that removing a field of 774 kV cm-1 yields a temperature change of -3.5 °C to -6.9 °C over a broad range of operating temperatures near room temperature (1-127 °C), with a correspondingly large refrigerant capacity of 662 J kg-1. In addition to low electrical hysteresis, there is negligible thermal hysteresis. PST thin films are therefore promising for EC cooling near room temperatu