dielectric spectroscopy and dielectric permittivity physical nature
DESCRIPTION
AACIMP 2011 Summer School. Science of Global Challenges stream. Lecture by Yuriy Poplavko.TRANSCRIPT
Dielectric Spectroscopyand
Dielectric Permittivity Physical Nature
Y. M. Poplavko
National Technical University of Ukraine, 37, Peremogi Ave., Kiev - 03056,
Ukraine
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Introduction 40 years of Dielectric Spectroscopy Dielectric Spectroscopy enables to
distinguish experimentally different polarization mechanisms.
Dielectric Spectroscopy studied fast and slow polarization mechanisms
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Historical excursus: 40 years of Dielectric Spectroscopy Y.M.Poplavko, V.G.Tsikalov, et al. Dielectric spectrum
of lithium niobate crystal. Physika Tverdogo Tela, 1973, Vol.15, No 5, p.1443.
Y.M.Poplavko, L.P.Pereverzeva et.al. Dielectric spectrum of TGS crystals. Physika Tverdogo Tela, 1973, Vol.15, No 4, p.1250.
Y.M.Poplavko, L.P.Pereverzeva et al. Dielectric spectrum of KDP type crystals. Kristallographija, 1973, Vol.18, No3, p.645.
Y.M.Poplavko et al. Rochelle salt dielectric spectrum at 1 Hz – 300 GHz. Phys. Tverdogo Tela, 1973, Vol.15, No8, p.2515.
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Dielectric permittivity nature
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Dielectric Spectroscopy methods
Microwave Dielectric Spectroscopy method is used: - in the frequency range of 0.1 – 100 GHz - in broad temperature interval of 80 – 800 K - a family of *(,T) = '(,T) + i "(,T) curves are
obtained. - spectra of order-disorder type ferroelectrics; - spectra of displace ferroelectric - spectra of solid solutions with the diffused phase
transition
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Examples of dielectric spectra
Dielectric spectra of various crystals and polarizationmechanisms: opt – electronic displace; IR – ionic; dip –dipole; EM – electromechanical; EC –electrocaloric.
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KDP crystal spectrum
Dielectric spectra of KH2PO4 crystal for 33
at T =150K with piezoelectric clamping:X – free stress samples;x – free strain samples.
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BaTiO3 crystal spectrum
Dielectric spectrum of ferroelectric phase ofBaTiO3 single crystal for the
11 at 290Kwithpiezoelectric clamping:
X – free stress samplesx –free strain samples:
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Electromechanical mechanism
Piezoelectric influence on KDP
eff = X
Piezoelectric influence on Salt and Rochelle
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Typical dielectric spectrum for order–disorder ferroelectrics
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Typical dielectric spectrum for displacive ferroelectrics
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Typical dielectric spectrum for relaxor ferroelectrics
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Relaxor ferroelectric PMN = PbMg1/3Nb2/3O3
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Microwave methods for ferroelectrics study
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Measurement scheme: a) short-circuit line method, b) transmission/reflection method
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Measured data and processing for TiO2, = 96
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Measured data and processing for 3.89 mm SrTiO3, transmission experiment
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Microwave methods for ferroelectric films study
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Schematic representation of film study experiment
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Measured data and calculation for ) 0.84 m BST film on 0.5 mm thickness MgO substrate.
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Coplanar line measurement cell
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Measured and calculated frequency dependence of scattering matrix parameter
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Thank you for kind attention!