Dielectric Spectroscopyand

Dielectric Permittivity Physical Nature

Y. M. Poplavko

National Technical University of Ukraine, 37, Peremogi Ave., Kiev - 03056,

Ukraine

2

Introduction 40 years of Dielectric Spectroscopy Dielectric Spectroscopy enables to

distinguish experimentally different polarization mechanisms.

Dielectric Spectroscopy studied fast and slow polarization mechanisms

3

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.

4

Dielectric permittivity nature

5

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

6

Examples of dielectric spectra

Dielectric spectra of various crystals and polarizationmechanisms: opt – electronic displace; IR – ionic; dip –dipole; EM – electromechanical; EC –electrocaloric.

7

KDP crystal spectrum

Dielectric spectra of KH2PO4 crystal for 33

at T =150K with piezoelectric clamping:X – free stress samples;x – free strain samples.

8

BaTiO3 crystal spectrum

Dielectric spectrum of ferroelectric phase ofBaTiO3 single crystal for the

11 at 290Kwithpiezoelectric clamping:

X – free stress samplesx –free strain samples:

9

Electromechanical mechanism

Piezoelectric influence on KDP

eff = X

Piezoelectric influence on Salt and Rochelle

10

Typical dielectric spectrum for order–disorder ferroelectrics

11

Typical dielectric spectrum for displacive ferroelectrics

12

Typical dielectric spectrum for relaxor ferroelectrics

13

Relaxor ferroelectric PMN = PbMg1/3Nb2/3O3

14

Microwave methods for ferroelectrics study

15

Measurement scheme: a) short-circuit line method, b) transmission/reflection method

16

Measured data and processing for TiO2, = 96

17

Measured data and processing for 3.89 mm SrTiO3, transmission experiment

18

Microwave methods for ferroelectric films study

19

Schematic representation of film study experiment

20

Measured data and calculation for ) 0.84 m BST film on 0.5 mm thickness MgO substrate.

21

Coplanar line measurement cell

22

Measured and calculated frequency dependence of scattering matrix parameter

S21

23

Thank you for kind attention!