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Dr. Ang Chen's Lab
Ferroelectric Relaxor Behavior
The “ferroelectric relaxors” behavior, which show a rounded permittivity peak, a low frequency dispersion and the temperature of the permittivity maximum increases with increasing frequency, was firstly observed by Smolenskii et al. in the Ba(Ti,Sn)O3 solid solution in 1954.[1] Later, the same phenomenon was also found in Pb(Mg1/3Nb2/3)O3, Pb(Sc1/2Ta1/2)O3 compounds by the same group.[2] Smolenskii et al. named this phenomenon as a Diffuse Phase Transition (DPT).[2]
In the earlier studies during 1960´s and 70´s, Smolenskii et al. proposed that the compositional heterogeneity on the cation site (or compositional fluctuation) was responsible for DPT.[2] However Smolenskii´s model cannot explain why the temperature of the permittivity maximum increases with increasing frequency. In 1980, Setter and Cross reported that order-disorder transitions had great influence on the relaxor behavior.[3] In 1983, based on the study on the ferroelectric relaxor (Pb,La)(Zr,Ti)O3, Yao, Chen and Cross suggested that the existence of micro-domains was essential to understand DPT and the dielectric relaxation behavior, and a micro- to macro- domain transition occurred in the relaxor.[4] The work shows the local polar clusters play an important role in “relaxors”. In 1987, Cross proposed that in relaxor, the nanometer-scale polar regions were dynamic in nature with the dipole moment thermally fluctuating between equivalent directions, and the ferroelectric relaxors were, in some way, electrical analogues of the superparamagnets, the so-called superparaelectrics.[5] Pure superparaelectrics predict a Debye-type relaxation behavior, which however gave physically unreasonable parameters for PMN. Due to this, a modified model, i.e. the “dipolar-glass” model, was proposed for the ferroelectric relaxors by Viehland and Cross et. al. In this model, the correlation between polar clusters was taken into account in analogy to the spin glass systems [6]. While, Westphal and Kleemann et al. [7] attributed the rounded permittivity peaks with frequency dispersion in PMN to the presence of domain states induced by quenched random fields. They argued that the ground state of the PMN is ferroelectric, and the random fields induced by the compositional fluctuation lead to the occurrence of domain states.
One question has been raised, is the ferroelectric relaxor relevant to what the ground state of materials is, ferroelectric or paraelectric?
To answer this question, please see, CHEN Ang, ZHI Yu, and ZHI Jing, Impurity induced ferroelectric relaxor behavior in quantum paraelectric SrTiO3 and ferroelectric BaTiO3, Physical Review B61, 957-961(2000). (The references [1] – [7] see also this paper’s references)
Other papers related this topic are also shown below.
CHEN Ang, ZHI Jing, and ZHI Yu, Ferroelectric relaxor Ba(Ti,Ce)O3, Journal of Physics: Condensed Matter, 14, 8901–12 (2002).
ZHI Yu, CHEN Ang, Ruyan Guo, and A.S. Bhalla, Ferroelectric-relaxor behavior of Ba(Ti0.7Zr0.3)O3, Journal of Applied Physics, 92[5], 2655-57 (2002).
ZHI Yu, CHEN Ang, E. Furman, and L. E. Cross, Dielectric relaxation and strain behavior of 95.5% Pb(Zn1/3Nb2/3)O3 – 4.5% PbTiO3 single crystals at cryogenic temperatures, Applied Physics Letters, 82[5], 790-792 (2003).
ZHI Jing, ZHI Yu and CHEN Ang, Crystalline structure and dielectric behavior of Ba(Ti,Ce)O3, Journal of Materials Science, 38[5], 1057-61 (2003).
CHEN Ang, ZHI Yu, ZHI Jing, Ruyan Guo, A.S. Bhalla, and L. E. Cross, Piezoelectric and Electrostrictive strain behavior of Ce-doped BaTiO3 ceramics, Applied Physics Letters, 80[18], 3424-26 (2002).
ZHI Jing, ZHI Yu and CHEN Ang, Crystalline structure and dielectric behavior of (Ce,Ba)TiO3 ceramics, Journal of Materials Research, 17 [11], 2787-2793 (2002).
ZHI Yu, CHEN Ang, Ruyan Guo, and A.S. Bhalla, Piezoelectric and strain properties of Ba(Ti1-xZrx)O3 ceramics, Journal of Applied Physics, 92[3], 1489-93 (2002).
ZHI Jing, CHEN Ang, ZHI Yu, P. M. Vilarinho and J. L. Baptista, Solubility of Y in BaTiO3 ceramics, Journal of American Ceramic Society (Rapid Communication), 82[5], 1345-48(1999).
ZHI Jing, CHEN Ang, ZHI Yu, P. M. Vilarinho and J. L. Baptista, Dielectric properties of Ba(Ti,Y)O3 ceramics, Journal of Applied Physics, 84, 983-986 (1998).