Magnetic control of relaxor features in BaZr0.5Ti0.5O3 and CoFe2O4 composite (original) (raw)
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A Brief Review on Relaxor Ferroelectrics and Selected Issues in Lead-Free Relaxors
Relaxor ferroelectricity is one of the most widely investigated but the least understood material classes in the condensed matter physics. This is largely due to the lack of experimental tools that decisively confirm the existing theoretical models. In spite of the diversity in the models, they share the core idea that the observed features in relaxors are closely related to localized chemical heterogeneity. Given this, this review attempts to overview the existing models of importance chronologically, from the diffuse phase transition model to the random-field model and to show how the core idea has been reflected in them to better shape our insight into the nature of relaxor-related phenomena. Then, the discussion will be directed to how the models of a common consensus, developed with the so-called canonical relaxors such as Pb(Mg 1/3 Nb 2/3)O3 (PMN) and (Pb, La)(Zr, Ti)O3 (PLZT), are compatible with phenomenological explanations for the recently identified re-laxors such as (Bi 1/2 Na 1/2)TiO3 (BNT)-based lead-free ferroelectrics. This review will be finalized with a discussion on the theoretical aspects of recently introduced 0−3 and 2−2 ferroelectric/relaxor composites as a practical tool for strain engineering.
High-T m relaxor ferroelectrics: 0.3BiScO 3 – 0.6PbTiO 3 – 0.1Pb " Mn 1Õ3 Nb 2Õ3 …O 3
High-T m relaxor materials are being developed for high-temperature high-power density electrotransduction applications and high-temperature capacitors in automobile applications. A relaxor ferroelectric material of composition 0.3BiScO 3 -0.6PbTiO 3 -0.1Pb(Mn 1/3 Nb 2/3 )O 3 having a very high dielectric maximum of ϳ350°C is reported. The relaxor behavior is confirmed by studying polarization relaxation and frequency and temperature dependent dielectric behavior. The dielectric constant in the low-temperature region of 10°CϽTϽ150°C is found to be independent of the frequency with a temperature gradient of ץ/ץTϭ2.5/°C. The room-temperature magnitude of dielectric constant is ϳ600.
Ceramics International, 2013
The electric field-induced strain of Bi 1/2 (Na 0.82 K 0.18 ) 1/2 TiO 3 (BNKT) ceramics modified with BaZrO 3 (BZ) was investigated as a function of composition and temperature. Unmodified BNKT ceramics revealed a typical ferroelectric butterfly-shaped bipolar S-E loop at room temperature, whose normalized strain (S max /E max ) showed a significant temperature coefficient of 0.38 pm/V/K. As the BZ content increased in the solid solution up to 5 mol%, the ferroelectric BNKT gradually transformed to a relaxor. Finally, 5 mol% BZmodified BNKT ceramics showed a typical electrostrictive behavior with a thermally stable electrostrictive coefficient (Q 33 )of0.025m 4 /C 2 , which is comparable to that of Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) ceramics that have been primarily used as Pb-based electrostrictive materials.
APL Materials, 2018
A thermotropic phase boundary between non-ergodic and ergodic relaxor phases is tuned in lead-free Bi1/2Na1/2TiO3-based ceramics through a structural transition driven by compositional modification (usually named as “morphotropic approach”). The substitution of Bi(Ni1/2Ti1/2)O3 for Bi1/2(Na0.78K0.22)1/2TiO3 induces a transition from tetragonal to “metrically” cubic phase and thereby, the ergodic relaxor ferroelectric phase becomes predominant at room temperature. A shift of the transition temperature (denoted as TF-R) in the non-ergodic-to-ergodic phase transition is corroborated via temperature-dependent dielectric permittivity and loss measurements. By monitoring the chemical composition dependence of polarization-electric field and strain-electric field hysteresis loops, it is possible to track the critical concentration of Bi(Ni1/2Ti1/2)O3 where the (1 − x)Bi0.5(Na0.78K0.22)0.5TiO3-xBi(Ni0.5Ti0.5)O3 ceramic undergoes the phase transition around room temperature. At the Bi(Ni0.5T...
A Transition From Relaxor To Normal Ferroelectric: An Overview
International journal of engineering research and technology, 2013
Relaxors like PMN and PMN based materials proved to be promising candidate for multilayer capacitors (MLCs) and electrostriction actuators , pyroelectric bolometers, piezoelectric sensors replacing normal ferroelectrics such as BaTiO 3 and PZT. The compositional heterogeneity resulting from scale of ordering at the B-site influences relaxor to normal ferroelectric behavior .The genesis and growth of PMR resulted in ferroelectric transition. The distribution of curie points in PMR leads to DPT behavior. The dielectric relaxation is attributed to the relaxation of domain walls. Strong charge effects developed as a result of 1:1 ordering at the B-site limits the ordering of domains hence the size growth. The difference between NFE and RFE along with mechanism influencing the transition from RFE to NFE have been discussed.
Solid State Sciences - SOLID STATE SCI, 2006
In order to investigate the effect of A-site homovalent and heterovalent substitution on phase transition in barium titanium zirconium oxide (Ba(Ti 0.7 Zr 0.3)O 3), dielectric studies were performed on ceramics of Ba 1−x A x (Ti 0.7 Zr 0.3)O 3 and Ba 1−x A 2x/3 (Ti 0.7 Zr 0.3)O 3 compositions (A = Ca, Sr; A = Y, La, Bi). A preliminary X-ray powder diffraction study has allowed us to determine the limits of solid solution for each composition. A relaxor behaviour appears whatever the value of x in the solid solution domains. The corresponding relaxor characteristics were determined and discussed according to the substituted cation in the twelve coordination number (12-C.N.) crystallographic site. Such new materials are of interest for environmental-friendly applications.
Study of the relaxor behavior in BaTi1−xHfxO3 (0.20≤x≤0.30) ceramics
Solid State Sciences, 2007
The influence of Hf doping on the structure and dielectric properties of BaTiO 3 has been studied. For this purpose Ba(Ti 1Àx Hf x )O 3 ceramics were prepared through solid-state reaction route at close compositions, having x ¼ 0.20, 0.22, 0.23 and 0.30. The study was aimed to locate the exact hafnium concentration for normal to relaxor crossover in these ceramics. X-ray diffraction followed by Rietveld refinement, reveals the formation of single phase with Pm3m cubic structure. Temperature and frequency dependence of real (3 0 ) and imaginary (3 00 ) parts of the dielectric permittivity have been studied in the temperature range of 90e350 K, at frequencies between 0.1 kHz and 100 kHz. The dielectric permittivity variations with temperature show deviation from CurieeWeiss behavior and strong frequency dispersion. The deviation from CurieeWeiss behavior, discontinuous jump along with the change in the slope of T m vs Hf concentration plot, and the degree of relaxation (g) approaching w2, indicate a crossover from normal to relaxor ferroelectrics. Substitution of Hf 4þ for Ti 4þ in BaTiO 3 introduces structural disorder, causing perturbations like local electric and strain fields. These perturbations reduce the long-range polar order resulting in relaxor behavior.
Bismuth zinc niobate: BZN-BT, a new lead-free BaTiO3-based ferroelectric relaxor?
Journal of Advanced Dielectrics, 2020
The novel lead-free ferroelectric relaxor system [Formula: see text](Bi([Formula: see text] [Formula: see text][Formula: see text](1[Formula: see text]BaTiO3 ([Formula: see text]BZN(1[Formula: see text]BT) has received interest as a high-capacity relaxor dielectric material. Small quantities (< 10.0 mol.%) of BZN-based dopant had significant impacts on the structure of the BaTiO3 host. This study evaluates the effect of BZN additions to the BaTiO3 host up to [Formula: see text]BZN = 10.0%. Initial additions of BZN were observed to stabilize tetragonal and orthorhombic coexistence at 295 K, alongside increasing dielectric constant. Peak dielectric constant and polarization were observed at [Formula: see text] < 4.0%, coinciding with maximum orthorhombic intensity and a local minima in tetragonal intensity. Compositions 0 < [Formula: see text] < 4.0% showed increasing polarization and a drop in [Formula: see text] and classical ferroelectric properties. No significant diel...