著名铁电物理学家L.E. Cross最新

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Єm ≈ 20,000 No macroscopic phase change Vogel:Fulcher glassy freezing: Evidence of nano-polar regions above Tm
Importance of Disorder evidence in Pb(Sc1/2Ta1/2)O3 Perovskite proper ferroelectrics: improper ferroelastics
X-ray diffraction and optical birefringence in lead magnesium niobate indicating the absence of any macroscopic phase change below the dielectric maximum at Tm
TUNGSTEN BRONZE STRUCTURE BARIUM STRONTIUM NIOBATE IS A PURE FERROELECTRIC RELAXOR
MODIFIED Ti50-xNi50+X MARTENSITIC SYSTEM JUST SHOWN TO BE A PURE RELAXOR FERROELASTIC
Evidence of glass like slowing down of the relaxation in lead magnesium niobate following Vogel: Fulcher low to a freezing temperature Tf
f = fo e
K
Ea (Tmax
Dependence ε = f (T) of PbMg1/3Nb2/3O3 monocrystal in frequency range 10-2 ~ 106
c/sec
Dependence 1/ε on (T-T0)2 for PbMg1/3 Nb2/3O3 monocrystal
G. A. Smolensky Proceeding of the second International Meeting on Ferroelectricity Kyoto Japan 1969 Supplement to J. Phys. Soc. Japan 28.58.1970
• Relaxor Ferroelectric: Lead titanate solid solution single crystals: Why so effective Macro-polarization rotation Much more effective than in normal ferroelectrics New evidence from thermal measurements
• Relaxor Ferroics • Extrinsic contributions to response in Ferroics
Relaxor Ferroics
• Classic Features of Relaxor Ferroelectrics Combine high permittivity levels of a ferroelectric with massive dielectric dispersion Initiated by G. A. Smolensky. Ferroelectrics with diffuse phase transitions. Identified Lead Magnesium Niobate Pb(Mg1/3 Nb2/3)O3 Classic Perovskite structure relaxor
Growth Points in Ferroic Studies
L. Eric Cross Materials Research Institute The Pennsylvania State University University Park, PA 16802 USA
Two areas where exciting things are happening which are of strong interest to:
PEROVSKITE STRUCTURE FERROELECTRICS ARE PROPER FERROELECTRICS
ELECTRIC POLARIZATION IS THE ORDER PARAMETER FOR THE FERROELECTRICS PHASE CHANGES
SOME OF THE DOMAIN STATES DIFFER IN SPONTANEOUS STRAIN. SO THAT THESE FERROELECTRICS ARE ALSO PARTIAL IMPROPER FERROELASTIC
Tf
Байду номын сангаас
Ea = 0.0407 eV
fo = 1.03.1012 Hz Tf = 291.5 K
Consequences of thermal ordering of the scandium tantalum cations in lead scandium tantalate (a) Polarization properties (b) Weak Field dielectric response (c) Optical anisotropy
• First pure Relaxor Ferroelastic Modified Nickel: Titanium metallic Martensite with excess nickel Elastic Dispersion in compliance Stress induced Martensite. Shape memory Massive high field compliance Vogel: Fulcher glassy freezing
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