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1 Oct 2000

Volume 88, Issue 7, pp. 3795-4457

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Pulsed laser deposition of relaxor-based PbLu0.5Nb0.5O3–PbTiO3 thin films

M. Tyunina, J. Levoska, S. Leppävuori, R. Shorubalko, and A. Sternberg

J. Appl. Phys. 88, 4274 (2000); http://dx.doi.org/10.1063/1.1290452 (8 pages) | Cited 5 times

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Ferroelectric thin films of relaxor-based PbLu0.5Nb0.5O3–PbTiO3 solid solution (PLuNT) with compositions near the morphotropic phase boundary were formed by in situ pulsed laser deposition onto La0.5Sr0.5CoO3/(100)MgO (LSCO/MgO). The phase composition of the PLuNT films was sensitive to the deposition temperature (550–710 °C), with single-phase perovskite formation only at 690 °C. The perovskite PLuNT films were pseudocubic and epitaxial, with (001) planes parallel to the substrate surface. At room temperature, capacitors Au/PLuNT/LSCO exhibited ferroelectric behavior (maximum polarization Pm≅29 μC/cm2, remnant polarization Pr≅14 μC/cm2, coercive field Ec≅70 kV/cm), and zero-field dielectric permittivity about ϵ≅300–450. A broad peak in ϵ was observed around 350 °C. With increasing deposition temperature, although the volume fraction of the pyrochlore phase decreased, Pm, Pr, and Ec all decreased, while ϵ remained unchanged. The suppression of polarization in the capacitors, both compared to that in the PLuNT ceramics and under the variation of the deposition temperature, was explained by the presence and evolution of passive layers near the electrodes. © 2000 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
84.32.Tt Capacitors
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)

Role of iron in lithium-niobate crystals for the dark-storage time of holograms

I. Nee, M. Müller, K. Buse, and E. Krätzig

J. Appl. Phys. 88, 4282 (2000); http://dx.doi.org/10.1063/1.1289814 (5 pages) | Cited 31 times

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The dark decay of holograms stored in iron-doped photorefractive lithium-niobate crystals is studied for samples containing up to 0.25 wt% Fe2O3 (iron concentration 71×1018 cm−3). The oxidation/reduction state of the crystals, i.e., the concentration ratio of Fe2+ and Fe3+ ions, is changed in a wide range by thermal annealing. The dark decay is attributed to two effects: An ionic dark conductivity arising from mobile protons and an electronic dark conductivity caused by tunneling of electrons between iron sites. The latter is proportional to the effective trap density, i.e., to the density of charge carriers which can be moved between the iron sites. The proportionality factor is the specific dark conductivity which increases exponentially with the third root of the entire iron concentration. © 2000 American Institute of Physics.
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42.70.Ln Holographic recording materials; optical storage media
42.40.Lx Diffraction efficiency, resolution, and other hologram characteristics
72.40.+w Photoconduction and photovoltaic effects
61.72.S- Impurities in crystals
42.79.Vb Optical storage systems, optical disks
66.30.H- Self-diffusion and ionic conduction in nonmetals
71.55.Ht Other nonmetals
42.40.Eq Holographic optical elements; holographic gratings

Optimal bounds on electric-field fluctuations for random composites

Robert Lipton

J. Appl. Phys. 88, 4287 (2000); http://dx.doi.org/10.1063/1.1290734 (7 pages) | Cited 2 times

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The electric field inside a two-phase composite is studied when the composite sample is subjected to a constant applied electric field. Upper and lower bounds on the covariance tensor of the electric field are found in terms of the effective dielectric properties of the composite. The lower bounds are shown to be optimal for two well-known families of microgeometries. Lower bounds on the covariance tensor are found when only the phase area fractions and the two-point correlation function are available. For statistically isotropic composites optimal lower bounds are derived when only the phase area fractions are known. © 2000 American Institute of Physics.
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77.22.Ch Permittivity (dielectric function)

Alternating current conduction behavior of excimer laser ablated SrBi2Nb2O9 thin films

S. Bhattacharyya, S. S. N. Bharadwaja, and S. B. Krupanidhi

J. Appl. Phys. 88, 4294 (2000); http://dx.doi.org/10.1063/1.1287782 (9 pages) | Cited 21 times

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Bi-layered Aurivillius compounds prove to be efficient candidates of nonvolatile memories. SrBi2Nb2O9 thin films were deposited by excimer laser ablation at low substrate temperature (400 °C) followed by an ex situ annealing at 750 °C. The polarization hysteresis behavior was confirmed by variation of polarization with the external applied electric field and also verified with capacitance versus voltage characteristics. The measured values of spontaneous and remnant polarizations were, respectively, 9 and 6 μC/cm2 with a coercive field of 90 kV/cm. The measured dielectric constant and dissipation factors at 100 kHz were 220 and 0.02, respectively. The frequency analysis of dielectric and ac conduction properties showed a distribution of relaxation times due to the presence of multiple grain boundaries in the films. The values of activation energies from the dissipation factor and grain interior resistance were found to be 0.9 and 1.3 eV, respectively. The deviation in these values was attributed to the energetic conditions of the grain boundaries and bulk grains. The macroscopic relaxation phenomenon is controlled by the higher resistive component in a film, such as grain boundaries at lower temperatures, which was highlighted in the present article in close relation to interior grain relaxation and conduction properties. © 2000 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.55.-g Dielectric thin films
73.61.Le Other inorganic semiconductors
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