Class 9: Polar materials and ferroelectricsseshadri/2016_286G/Polar1.pdf · 2016. 4. 20. · Class...
Transcript of Class 9: Polar materials and ferroelectricsseshadri/2016_286G/Polar1.pdf · 2016. 4. 20. · Class...
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
Valasek, 1921
From Megaw, Ferroelectricity in Crystals.
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
Hydrogen-bonded ferroelectricityin Rochelle’s salt.
From Megaw, Ferroelectricity in Crystals.
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
From Megaw, Ferroelectricity in Crystals.
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
From Megaw, Ferroelectricity in Crystals.
Hydrogen-bonded ferroelectricity in potassium dihydrogen phosphate (KDP).
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
From Megaw, Ferroelectricity in Crystals.
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
From Megaw, Ferroelectricity in Crystals.
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Eg
A1g Splitting of the structural soft mode (Raman active below Ta)
Ta
Class 9: Polar materials and ferroelectrics Antiferrodistortive transition in SrTiO3 in R-point of the Brillouin
zone
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Ferroelectric SM
Structural SM (doublet)
Mode frequencies on STO ceramics
(Petzelt et al., PRB 64, 184111 (2001))
Class 9: Polar materials and ferroelectrics
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Class 9: Polar materials and ferroelectrics
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
SrTiO3 ceramicsClass 9: Polar materials and ferroelectrics
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
0 50 100 150 200 250 300
1000
10000
SrTiO3
Temperature (K)
ε 0Experiment:
crystal (Hyper-Raman) 2 μm-grained ceramics (BWO) 2 μm-grained ceramics (MW) 100 nm-grained ceramics (diel. meas. 100 kHz)
Theoretical model: 2 μm-grained ceramics, eps(GB)=100, ξ= 7 nm 100 nm grained, eps(GB)=100, ξ= 7 nm
Class 9: Polar materials and ferroelectrics
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Order-disorder model forBaTiO3 phase transitions
Class 9: Polar materials and ferroelectrics
Dynamically disordered Ti
Ordered Ba
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
0 200 400 600 800 1000 1200 14000
20406080
100120140160180200220240260280
CTR O
E
E
Freq
uenc
y (c
m-1)
Luspin_80 (IR refl.) Vogt_82 (HR) Laabidi_90 (R) Perry_65 (R) Burns_78 (R) Dougherty_94 (femt. ISRS)
Temperature (K)
B2
B1?
A1
F1u
TO1 mode in BaTiO3 single crystal
Class 9: Polar materials and ferroelectrics
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Materials 286 G: Structural Families of Functional Inorganic MaterialsRam Seshadri x6129 seshadri@mrl
Unpolarized Raman spectra of BaTiO3 crystals (after Perry and Hall 1965)
Wavenumber (cm-1)
Class 9: Polar materials and ferroelectrics
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