EPR, ENDOR and ESE investigations on chromium modified PbTiO3 ceramics

Böttcher, R.; Brunner, W.; Milsch, B.; Völkel, G.; Windsch, W.; Kirillov, S. T.

doi:10.1016/0009-2614(86)80398-0

Cited by 19 publications

(9 citation statements)

References 5 publications

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“…2) measured at room temperature reveals in the middle of the spectrum (g D 1.94) a multi-line pattern, which is to be attributed to Cr 5C (S D 1/2) probe ions. 19 Though being quite conspicuous, this partial spectrum is only of minor importance here: It largely disappears at about 400 K and, hence, does not furnish any information about the temperature-or size-driven phase transition. Furthermore, seven peaks lying outside of the central part of the spectrum are observed.…”

Section: Crmentioning

confidence: 96%

Size effects in chromium-doped PbTiO3 nanopowders observed by multi-frequency EPR

et al. 2005

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A multi-frequency (X, Q, and W band) electron paramagnetic resonance (EPR) study of Cr-doped PbTiO3 micro- and nanopowder samples was performed. Three Cr3+ centres were identified in tetragonal phase samples with different axial Zero Field Splitting (ZFS) parameters, C1, C2, and C3. The centre C1 is similar to that observed in previous X-band crystal and ceramic sample measurements. The superposition model by Newman and Urban was applied to translate the ZFS data into local displacements inside the distorted oxygen octahedra of the PbTiO3 lattice. In the tetragonal phase, only the centre C1 was observed. The powder spectra were fitted using a spin-Hamiltonian in which a Gaussian distribution of ZFS terms, characterized by a mean value D and distribution width deltaD, was assumed. The variation of D and deltaD with mean particle size was determined. A critical particle size, d(cr), exists, particles smaller than this size remain in the cubic phase for all temperatures, there is a size-driven tetragonal-to-cubic phase transition. Particles with d < d(cr) were found to give a new Cr3+ centre spectrum, C4, consisting of a single line with an isotropic g-factor, so allowing the cubic phase content to be quantified. Further, temperature-dependent EPR measurements were made, which allowed the variation in Curie temperature with mean particle size to be determined.

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Section: Crmentioning

confidence: 96%

Size effects in chromium-doped PbTiO3 nanopowders observed by multi-frequency EPR

et al. 2005

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“…However, the values strongly vary when changing from lead titanate (g zz D 2.332 š 0.001, A 2C coordinated by six ligands that form an elongated octahedron. This can be understood in terms of a fivefold orbital degeneracy of the 3d 9 ion that is lifted in the presence of an octahedral crystal field, yielding a triplet (t 2g and a doublet (e g , with the latter lying lowest. The lattice distortion splits the e g levels further, resulting in an orbital-singlet d 3 , the X-band EPR spectrum, depicted in Fig.…”

Section: + -Modified Pztmentioning

confidence: 99%

High-field/high-frequency EPR of paramagnetic functional centers in Cu2+- and Fe3+-modified polycrystalline Pb[ZrxTi1−x]O3 ferroelectrics

et al. 2005

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Copper(II)- and iron(III)-modified Pb[Zr(x)Ti(1-x)]O3 ferroelectrics were investigated by means of high-field/high-frequency EPR. The results obtained suggest that Cu2+ and Fe3+ both substitute as acceptor centers for [Zr,Ti]4+. Whereas for the iron-doped system the charge compensating oxygen vacancies (V(O)**) lead to the formation of charged (Fe'(Ti-)V(O)**)* defect associates, no such associates have been observed for the copper-modified system. As regards the morphotropic phase boundary, the model of a mesoscopic mixing of the pure-member phases has been refined to a picture in which a nanoscale composition distribution prevails.

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“…The method-of-choice to characterize these paramagnetic dopants is provided by electron paramagnetic resonance (EPR) spectroscopy. Although EPR has been applied for many decades to study transition-metal centers in singlecrystal type perovskite oxides, recent methodological progress concerning the use of high frequencies [39][40][41][42][43][44][45][46][47][48][49][50] and pulsed microwave fields 14,[51][52][53][54][55][56][57] have allowed for an enhanced spectral resolution and thus provided additional insight in the prevailing defect structure. Therefore, spin-Hamiltonian parameters for technologically relevant ceramic compounds can now be determined to a similar accuracy as compared to model-type single crystals, which considerably differ from their ceramic counterparts with respect to processing conditions and dopant concentrations.…”

Section: Introductionmentioning

confidence: 99%

Structural and dynamic properties of oxygen vacancies in perovskite oxides—analysis of defect chemistry by modern multi-frequency and pulsed EPR techniques

Eichel

2011

Phys. Chem. Chem. Phys.

221

145

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Multi-frequency and pulsed electron paramagnetic resonance (EPR) provides a sensitive spectroscopic tool to elucidate the defect structure of transition-metal doped perovskite oxides, as well as to monitor dynamic processes of oxygen vacancies in these materials. In this regard, high-frequency EPR spectrometers and pulsed EPR techniques such as the hyperfine sublevel correlation experiment (HYSCORE) may now routinely be used for dedicated investigations, providing considerably more insight than the application of standard continuous-wave EPR. Recent results include the formation of defect complexes between acceptor-type transition-metal centers with either one or two oxygen vacancies for the reason of charge compensation. Furthermore, such defect complexes follow the domain switching upon poling ferroelectric compounds with correspondingly high electric fields. On the other hand, multi-valent manganese functional centers provide trapping centers for electronic and ionic charge carriers (e', ) such that valency altered acceptor states or defect complexes are formed. Additionally, the trapping of charge carriers at the intrinsic 'reduced' B-site ions, and , can be observed by means of EPR spectroscopy.

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EPR, ENDOR and ESE investigations on chromium modified PbTiO3 ceramics

Cited by 19 publications

References 5 publications

Size effects in chromium-doped PbTiO3 nanopowders observed by multi-frequency EPR

Size effects in chromium-doped PbTiO3 nanopowders observed by multi-frequency EPR

High-field/high-frequency EPR of paramagnetic functional centers in Cu2+- and Fe3+-modified polycrystalline Pb[ZrxTi1−x]O3 ferroelectrics

Structural and dynamic properties of oxygen vacancies in perovskite oxides—analysis of defect chemistry by modern multi-frequency and pulsed EPR techniques

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