????? Basics of Ferroelectrics

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?????Basics of Ferroelectrics
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• ??????,
• ????,Sawyer-Tower ??
• ???????
• ??????????????
• ???????,
• ????

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????

• ????????(Ps)
• Spontaneous Polarization
• ???????????????,??????
• Switchable Ps,or reorientated Ps

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Note

• ??????????????????????????,??????????,????????
  ?????
• ?????(??????)????????????(Seignett-electricity
  )??????(Rochell-electricity)?
• ?????????????????1920????Valasek????????,?????????
  ?????????????1665??????????????????????????

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????

• ???? Hysteresis loop
• ???? Curie temperature Tc
• ???? Dielectric anomalous

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???? hysteresis loop
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• ????Ps
• Spontaneous Polarization
• ????Pr
• Remnant Polarization
• ????Ec
• Coercive field

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Sawyer-Tower ??
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• ???????????????????????????,????????????????
• ??????????????,?????????????????
• ??????????????????????,???????????????
• ??????????,?????????????????,?????????????????????
  ???

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Domain in ceramic samples
???
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???? (Tc)

• ??????????Tc?,??????????(??????)??????????????Tc?,
  ????????,????Tc?,?????????????????????????????????
  ??,??????????????????????????????????????,????-???
  ?????????????????????????????????????????

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????????

• ??????????????????????????????????????,??????????
  ????????????????????,??????????????,?????????????
  ????????????????,?????????????????????????????????
  ???????,??????,104-105,????????????????

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??-???? Curie-Weiss law

• ?????????,??????????????????-????

??C???-????T?????T0???????,????-?????
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??????????

• BaTiO3,???
• KDP,????? KH2PO4
• TGS,???????,(NH2CH2COOH)3 H2SO4
• RS,?????(???)NaKC4H4O64H2O

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Spontaneous polarization of BaTiO3
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Dielectric constant of BaTiO3
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????????????????
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KDP???????????????
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KDP?????????????
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KDP???????????
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KDP???????d36??????
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TGS???????????????
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TGS???????????????
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TGS???????????
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??????????????????
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????-??(La Rochelle)
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????????????????
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RS?????????S44??????
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???????

• ?????????????????
• ???????????????????10?????
• ??????????10-4C/m2?1C/m2??????????-261.5C(?????)
  ,????1500C?

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• ?6-1?????????????????????????
• ?????????????????????,??????????????????
• ?????,?????????????,???????????

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?????,?????

• ???????????????????????????????????,????????????,?
  ????????,??????????????????????????????(??????????
  ????),?????????????????????????????

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???????

• ???????????????????????
• ??????????????????????,??????????????????KDP????
• ??????,???????????????,?????????,?????????????????
  ?????????????????????

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?????

• ???????????,?????????????????????,?KDP??TGS???????
  ??????????????????????????????,?????????????????
  ,?????????????????????????????????????????,?????
  ???

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??-????

• ???-?????????(???6-4),?????????????????????-????C
  ???105??????????????????????????,?????????????????
  ?????SbSI??????????,???????

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• ??-????C ???103????????,????????????????-???,????K
  DP?TGS?????NaNO2??C??????10?????????,???????????(N
  H4)2Cd2(SO4)3???????????????????,????????

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?6-4 ??????-???????
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????? Quantum Paraelectrics

• ?????? Incipient Ferroelectrics
• ?????SrTiO3,
• ??? CaTiO3 , KTaO3
• ????????????????,??????????,????????????
• ????????????????????????????

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K A Muller, Jpn J Appl Phys 24 (1985) 24-2,
pp.89-93 Quantum Para- , Ferro-, and Random
Electric Behaviors in Oxide Perovskites
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????? ferroelectric relaxor

• ????????????,???????????,??????????????,??????????
  ??
• ??????????????????????
• ???????????????????????,????????,??????

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• ??????????????-????,????????-????
• ???????????,???????????????????????????
• ?????,???????????????
• ??????????,??????????

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• ???????? Pb(Mg1/3Nb2/3)O3,????Pb(Zn1/3Nb2/3)O3
  ,B-????????(complex perovskite)
• ???? (Na1/2Bi1/2)TiO3,A-????????
• ?????????(tungsten bronze)

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Kighelman, Damjanov and N Setter, J Appl Phys
90(2001) 4684
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G A Smolenski, J Phys Soc Jpn 28Supl (1970) 26
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????? ferroelectric polymers

• ?????(Polyvinyleden fluoride),PVDF,PVF2, ???
  -(CH2CF2)n-
• ??,??a???? -gt b?,???????
• ???????-(CHCF3)n-,PVDF-TrFE,???????????
• ??????,??????????

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???? Anti-ferroelectrics
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• ???????????,????????????,?????????????????,???????
  ??,???????????????????(????)??????????????,??????
  ,??????10-102??????,????????,????????????????,???
  ???????????-?????

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• x-??????,???????,???????????(???????)?????????????
  ,????????????????,??????????????
• ???????
• ?????(NH4H2PO4),
• ???(PbZrO3)

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PbZrO3????????????
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??????????????????
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• ??????????
• ??????????????,???????????????????????????????????
  ???????????(????PbZrO3??WO3????)??????????????????
  ?????????PbZrO3?????????

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????????????????????????
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??? ferroics

• ?????????????????
• ?????????
• ?????????

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Summary

• ferroelectricsspontaneous polarization, and
  switchable under external field features
  hysteresis loop, Curie temperature, critical
  phenomenon
• Typical ferroelectrics BaTiO3, KH2PO4
• Displacive and order-disorder type of
  ferroelectrics, uniaxial and multiaxial
• Quantum paraelectrics, ferroelectric relaxor,
  ferroelectric polymer
• Antiferroelectrics, and ferroics, multiferroics