Dielectric and ferroelectric behavior of cerium modified SrBi2Ta2O9 ceramic
Introduction
Aurivillius structured materials, the so-called bismuth layer structured ferroelectrics (BLSFs), have aroused much interest in the recent years due to their potential application in technical devices, e.g. in non-volatile ferroelectric random access memory (FE-RAM) [1], [2], [3], [4]. SrBi2Ta2O9 ferroelectric has been extensively investigated as a promising candidate for nonvolatile ferroelectric random access memories, because of high fatigue endurance (up to 1011 to 1012 switching cycles), good retention characteristics, low switching fields, and low leakage current [5], [6], [7], [8]. It is widely accepted that the Bi2O2 layers have a significant influence on the polar and electrical conductivity properties of bismuth based layered structures. There has been a lot of research conducted to enhance their properties by the substitution of the Bi3+ ions of rare earth cations [9], [10], [11], [12], [13], [14]. The effect of CeO2 on various ceramics has been extensively studied because of their high endurance under DC field stress, grain growth inhibition, and the effective Curie temperature shift. The valence states of cerium ions vary between trivalent (Ce3+) and tetravalent (Ce4+), depending on the starting formula and the sintering atmosphere [15]. Therefore, it is expected that by substituting Bi3+ ion with the large difference in the eightfold coordination ionic radii of Ce4+ ion in the crystal lattice of SBT ferroelectrics could enhance its physical properties. The effect of Ce doping on the structural, electrical and optical properties of SrBi2−xCe3x/4Ta2O9 (where x=0.00, 0.025, 0.05, 0.075 and 0.10) ferroelectric ceramics have been studied in detail.
Section snippets
Experimental procedure
SrCO3, Bi2O3, CeO2 and Ta2O5 are used as starting raw materials which are weighed according to the stoichiometric ratio with the formula SrBi2−xCe3x/4Ta2O9 (x=0, 0.025, 0.05, 0.075 and 0.1) and ground in an agate mortar for 2 h. The mixed powder is ball milled in a laboratory ball milling machine using Zr ball in acetone medium. 3 wt% of excess Bi2O3 is added with calculated precursors to compensate the loss during sintering. The mixed precursors are calcined at 1000 °C for 4 h after drying
Structural analysis
Fig. 1 shows the XRD pattern of Ce doped SrBi2Ta2O9 ceramics calcinied at 1000 °C for 4 h. All the prominent peaks show the characteristic nature of single phase Bi-layered (m=2) Aurivillius compounds with A21am orthorhombic symmetry and are well agreed with the Joint Committee on Powder Diffraction Standards (JCPDS no 49-0609) card. The variation of lattice parameter is calculated by the MDI Jade5.0 program and shown in the inset of Fig. 1. The Ce4+ incorporation may change the type of bonding
Ferroelectric properties
The well saturated P–E hysteresis loop of Ce doped SrBi2Ta2O9 ceramics at room temperature is shown in Fig. 4. It is observed that the Pr value increases and the Ec value decreases with increase in Ce content. Similar kind of improvement due to influence of rare-earth ion substitution in simple perovskite ferroelectrics have shown improved ferroelectric properties [19]. The substitution of rare earth in SBT produces oxygen vacancies with the ceramic. Oxygen vacancies produced by the replacement
Conclusion
Cerium modified SBT ceramic has been prepared by solid state reaction route. The XRD plot shows that the all the compositions are of single phase. A reduction in the grain size with a plate like structure is observed from the SEM figures. The temperature dependent dielectric study revealed that the dielectric constant and the transition temperature decreases with increase in Ce content. The diffusivity of dielectric maximum is found to increase with cerium content. The ferroelectric property is
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2022, Journal of Materials Science and TechnologyCitation Excerpt :SrBi2Ta2O9 (SBTO) as a member of the Aurivillius family has a relatively negative conduction band (CB) position and the potential to reduce the organic pollutants. However, most works reported on SrBi2Ta2O9 mainly focus on their synthesis [23], thin-film [24], and ceramics [25]. The research is limited in visible-light-responsive photocatalysis application by its wide band gap and low overall efficiency [26].
Voltage control of millimeter-wave ferromagnetic resonance in multiferroic heterostructures thin films
2020, Physics Letters, Section A: General, Atomic and Solid State PhysicsCitation Excerpt :Then J. Das [11] grew a BaM-base heterostructure (Ba0.5Sr0.5TiO3/BaM), and reported that the ME coupling coefficient is 1.4 MHz cm/kV, but still it is not strong enough and they did not pay attention to the millimeter wave properties. However, strontium bismuth tantalate [12,13] (SrBi2Ta2O9, SBT) has a high electrostriction coefficient, good endurance and low switching voltage, together with a large permittivity that exhibits strong electric-field dependence and it is lead-free. Hence, SBT is used as a ferroelectric phase.
Review of the most common relaxor ferroelectrics and their applications
2018, Magnetic, Ferroelectric, and Multiferroic Metal OxidesElectrocaloric effect in lead-free Aurivillius relaxor ferroelectric ceramics
2017, Acta MaterialiaCitation Excerpt :Both ceramics show no traces of secondary phase. They are over 95% dense with elongated anisometric grains, typical for Aurivillius phases [21,22]. The grains are smaller in the case of the Pr-doped ceramics, which is consistent with the known fact that the rare earth dopants efficiently suppress the grain growth.
Impedance spectroscopy and photocatalysis water splitting for hydrogen production with cerium modified SrBi<inf>2</inf>Ta<inf>2</inf>O<inf>9</inf> ferroelectrics
2016, International Journal of Hydrogen EnergyCitation Excerpt :Therefore, it would be important to examine new photocatalysts with Aurivillius-type structure. The dielectric and ferroelectric properties of cerium modified SBT ferroelectric ceramics is reported elsewhere [16]. In this paper, the SrBi2-xCe3x/4Ta2O9 compounds are synthesized by solid–state reaction method.