Microstructural Evolution of Pb(Zr,Ti)O3 Ceramics Using Electron Paramagnetic Resonance

AbstractUsing electron paramagnetic resonance (EPR) we have followed the microstructural evolution with temperature of lead zirconate titanate (PZT) ceramics from the amorphous to the perovskite phase. A number of paramagnetic point defects were identified (Carbon, Pb+3, and Ti+3) while traversing the evolution of these ceramics during various heat treatments both before and after optical illumination. Perhaps the most important finding is that the Pb+3 and Ti+3 centers can only be optically created in the perovskite materials, thereby, showing that they are not associated with the amorphous or the pyrochlore phases. It is also found that EPR signals attributed to carbon radicals are present in fairly high concentrations (4 × 1017/cm3) if the solution chemistry derived PZT materials are annealed in an oxygen deficient ambient (0.1% O2) at 650°C.

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An Experimental Technique for Studying Chemisorption Reactions by Means of Electron Paramagnetic Resonance Spectroscopy

Applied Spectroscopy ◽

10.1366/000370272774352290 ◽

1972 ◽

Vol 26 (2) ◽

pp. 239-241 ◽

Cited By ~ 1

Author(s):

Eugene P. Scheide ◽

George G. Guilbault

Keyword(s):

Electron Paramagnetic Resonance ◽

Experimental Method ◽

Electron Paramagnetic Resonance Spectroscopy ◽

Cupric Chloride ◽

Resonance Spectroscopy ◽

Epr Spectrum ◽

Paramagnetic Resonance ◽

Before And After ◽

Chemisorption Bond ◽

Electron Paramagnetic

A new experimental method and a specially designed EPR cell are described for use in the study of chemisorption reactions. By studying the EPR spectrum of a surface both before and after chemisorption, it can be shown whether unpaired d electrons are used in the chemisorption bond and the nature of this bond. The EPR spectra of a cupric chloride surface, both before and after a gaseous ligand (diisopropyl methyl phosphonate) is chemisorbed, are shown and the results are interpreted in terms of the type of bond formed.

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Microstructural development in solution-derived PZT thin films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100170621 ◽

1994 ◽

Vol 52 ◽

pp. 578-579

Author(s):

T. J. Headley ◽

B. A. Tuttle ◽

J. A. Voigt ◽

J. R. Michael

Keyword(s):

Thin Films ◽

Lead Zirconate Titanate ◽

Capital Investment ◽

Perovskite Phase ◽

Amorphous Film ◽

Phase Evolution ◽

Lead Zirconate ◽

Solution Chemistry ◽

Microstructural Development ◽

Pzt Thin Films

Lead zirconate titanate (PZT) thin films are of technological interest for a variety of electronic and optical applications such as nonvolatile memories, decoupling capacitors, infrared detectors, and optical storage media. Fabrication of PZT films by solution deposition techniques is attractive because of uniform, stoichiometric control at the molecular level, ease of processing, and both low capital investment and total cost. Control of phase evolution, microstructure, crystallite size and orientation, and ferroelectric domain assemblage during processing is essential to optimize electrical and/or optical properties of the films. Factors which play a major role in controlling these parameters are details of the solution chemistry and mixing, thermal processing, Pb stoichiometry, Zr/Ti ratio, and substrate characteristics. Electron microscopy techniques have been used extensively to correlate microstructural features with film processing parameters as will be emphasized in this presentation.As annealing temperature is increased, phase evolution in PZT thin films typically proceeds from amorphous to pyrochlore to the ferroelectric perovskite phase. Fine-grained pyrochlore crystallizes from the amorphous film at low annealing temperatures and also precedes crystallization of the perovskite phase at higher temperatures. There is evidence that the Zr/Ti stoichiometry influences the microstructure of the amorphous-to-pyrochlore transformation.

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Electron Paramagnetic Resonance Study of Low Temperature Molecular Beam Epitaxy Grown GaAs and InP Layers

MRS Proceedings ◽

10.1557/proc-241-69 ◽

1991 ◽

Vol 241 ◽

Cited By ~ 2

Author(s):

H. J. von Bardeleben ◽

Y. Q. Jia ◽

J. P. Hirtz ◽

J. C. Garcia ◽

M. O. Manasreh ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Molecular Beam Epitaxy ◽

Low Temperature ◽

Molecular Beam ◽

Electron Paramagnetic Resonance Study ◽

Paramagnetic Resonance ◽

Native Defects ◽

Antisite Defects ◽

High Concentrations ◽

Electron Paramagnetic

ABSTRACTThe native defects in LTMBE III-V layers have been studied by the electron paramagnetic resonance (EPR) technique for three different systems: GaAs on GaAs, GaAs on Si and InP on InP. The GaAs layers are characterised by high concentrations of ionized arsenic antisite defects(1019 cm −3), with properties similar to those of the native AsGa in amorphous GaAs. Their variation with the growth temperature, layer thickness and thermal annealings has been assessed.The results are independant on the nature of the substrate, GaAs or Si. Inspite of a 1% phosphorous excess no phosphorous antisites could be detected in the as-grown, undoped or Be doped InP layers.

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Complex-formation between reduced xanthine oxidase and purine substrates demonstrated by electron paramagnetic resonance

Biochemical Journal ◽

10.1042/bj1140735 ◽

1969 ◽

Vol 114 (4) ◽

pp. 735-742 ◽

Cited By ~ 33

Author(s):

Frances M. Pick ◽

R C Bray

Keyword(s):

Electron Paramagnetic Resonance ◽

Xanthine Oxidase ◽

Active Site ◽

Paramagnetic Resonance ◽

Freezing Method ◽

Low Concentrations ◽

Appearance Rate ◽

High Concentrations ◽

Electron Paramagnetic ◽

Do So

The origin of the Rapid molybdenum electron-paramagnetic-resonance signals, which are obtained on reducing xanthine oxidase with purine or with xanthine, and whose parameters were measured by Bray & Vänngård (1969), was studied. It is concluded that these signals represent complexes of reduced enzyme with substrate molecules. Xanthine forms one complex at high concentrations and a different one at low concentrations. Purine forms a complex indistinguishable from the low-concentration xanthine complex. There are indications that some other substrates also form complexes, but uric acid, a reaction product, does not appear to do so. The possible significance of the complexes in the catalytic cycle of the enzyme is discussed and it is suggested that they represent substrate molecules bound at the reduced active site, waiting their turn to react there, when the enzyme has been reoxidized. Support for this role for the complexes was deduced from experiments in which frozen samples of enzyme–xanthine mixtures, prepared by the rapid-freezing method, were warmed until the signals began to change. Under these conditions an increase in amplitude of the Very Rapid signal took place. Data bearing on the origin of the Slow molybdenum signal are also discussed. This signal disappears only slowly in the presence of oxygen, and its appearance rate is unaffected by change in the concentration of dithionite. It is concluded that, like other signals from the enzyme, it is due to Mov but that a slow change of ligand takes place before it is seen. The Slow species, like the Rapid, seems capable of forming complexes with purines.

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