Antiferroelectric ceramic

Zhou, L., Zuo, R.Z., Rixecker, G., Zimmermarm, A., Utschig, T, and Aldinger, F. (2006) Electric fiitigue in antiferroelectric ceramics induced by bipolar electric fatigue. J. Appl. Phys., 99, 044102. 

PMMA/PZT Composites (Polar-Polymer/Antiferroelectric Ceramic Systems)... 

In lead zirconate, PbZr03, the larger lead ions are displaced alternately from the cube comer sites to produce an antiferroelectric. This can readily be converted to a ferroelectric by the substitution of Ti4+ ions for some of the Zr4+ ions, the maximum value of permittivity occurring at about the 50 50 mixture of PbZrC>3 and PbTiC>3. The resulting PZT ceramics are used in a number of capacitance and electro-optic applications. The major problem in the preparation of these solid solutions is the volatility of PbO. This is overcome by... 

In some perovskite ceramics, the instability that occurs at the Curie temperature is not ferroelectric but rather antiferroelectric. In antiferroelectric crystals, the neighboring lines of ions are displaced in opposite senses which creates two alternating dipole sublattices of equivalent but opposite polarization. Consequently, the net polarization is zero, and the dielectric constant does change at the transition temperature. Examples of antiferroelectric crystals are WO3, NaNbO, PbZrO, and PbHfOj. 

Finally we can note that the ferroelectric state of relaxors is characterised by an extremely narrow hysteresis loop with a low value for the remanent polarisation (Figure 6.19a). This sort of hysteresis loop can be considered to fall into the continuum described previously (Figure 6.9) and suggests that the microsttucture of the phases is at an even more reduced scale than the fine-grained ceramic samples. Indeed, the behaviour when the materials are either cooled in or without an external electric field (FC or ZFC) is also taken as indicative of a complex microstructure. The strain versus applied electric field loop has a U shape, rather like the central portion of the strain curve for an antiferroelectric (Figure 6.19b). 

Likewise, in lead lanthanum zirconate titanate (PLZT) relaxors, the substitution of La for Pb at A sites produces randomly distributed Pb vacancies. In bismuth sodium titanate (BNT [BiNa]Ti206), the replacement of Bi by Na creates charge imbalances and vacancies. Ceramics with compositions Bai, jNaxTii Nbx03 are either classical ferroelectrics (for 0relaxor ferroelectrics (for 0.075 < x< 0.055) with a diffuse transition temperature without any frequency dispersion. The relaxor behavior increases with increasing compositional deviation from both BaTi03 and NaNbOs (Khemahem et al., 2000). 

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