Electrical Investigations of Aurivillius Type Sr0.7A0.3Bi2Nb2O9 (A = Ca, La and Pb) Ferroelectric Ceramics

Synthesis and ferroelectric properties of bismuth layer-structured (Bi7−xSrx)(Fe3−xTi3+x)O21 solid solutions

Abstract: Bismuth layer-structured (Bi 7− x Sr x )(Fe 3− x Ti 3+ x )O 21 (BSFT) ceramics were synthesized and the ferroelectric properties and crystal structure were investigated. X-ray powder diffraction profiles and refinement of the lattice parameters indicated single phase BSFT was obtained in the composition range 0–1.5. The lattice parameter b of BSFT remained almost constant, while a slight decrease in the lattice parameter a was observed by the Sr and Ti substitution for Bi and Fe, respectively, which indicated an increase in the orthorhombicity. The dependence of the BSFT lattice parameter on temperature implied a phase transition from the orthorhombic to the tetragonal phase, which was in good agreement with the Curie temperature. The remnant polarization P r , of BSFT was significantly improved by the Sr and Ti substitution for Bi and Fe, and ranged from 9 to 16 μC/cm 2 , although no remarkable variation in the coercive field E c was observed. As a result, a well-saturated P – E hysteresis loop of BSFT ceramic was obtained at x =0.5 with a P r of 30 μC/cm at an applied voltage of 280 kV/cm.

Structural, Dielectric and Ferroelectric Studies of Molybdenum Substituted Sr2Bi2Nb2O9 Ferroelectric Ceramics

Abstract: In the present work, samples of compositions SrBi 2 Nb 2 O 9 and SrBi 2 Nb 1.9 Mo 0.1 O 9 were prepared by solid state reaction method. X ray diffraction analysis reveals the formation of single phase perovskite structure. Although the perovskite structure of SBN is retained but slight change in the lattice parameters is observed. Dielectric constant and dielectric loss have been measured as a function of temperature (300 K–800 K) and frequency (1 kHz, 10 kHz and 100 kHz). Peak Dielectric constant is observed to increase from 465.05 for pure SBN to 613.17 for molybdenum substituted SBN while Curie temperature is observed to decrease from 420°C for pure SBN to 365°C for molybdenum substituted SBN. Dielectric loss is observed to increase from 0.066 for pure SBN to 0.123 for the doped sample at their respective Curie temperature. P-E loops have been recorded and retentivity and coercevity have been determined. The coercive field and remanant polarization values are observed to decrease from 10.647 μzv/c.m. a...

Dielectric and electrical studies of SrBi 2 Nb 1.9 V 0.1 O 9 ferroelectric ceramics

Abstract: In the present work, effect of sintering temperature on structural, dielectric and electrical properties of vanadium substituted strontium bismuth niobate ferroelectric ceramics have been studied. Samples of composition SrBi 2 Nb 1.9 V 0.1 O 9 were synthesized by solid-state reaction method at different sintering temperatures. X - ray diffraction analysis reveals the formation of perovskite structure. Peak dielectric constant is found to increase with increasing sintering temperature while Curie temperature is observed to be the highest in the sample sintered at 900 °C and it decreases in the sample sintered at 1000 °C. Impedance analysis of the samples was carried out to study the grain and the grain boundary effects. Cole-cole plots reveal a decrease in bulk resistance on increasing temperature indicating NTCR behavior.

CRC Handbook of Chemistry and Physics

Abstract: CRC handbook of chemistry and physics , CRC handbook of chemistry and physics , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

Ferroelectric ceramics : History and technology

Abstract: Ferroelectric ceramics were born in the early 1940s with the discovery of the phenomenon of ferroelectricity as the source of the unusually high dielectric constant in ceramic barium titanate capacitors. Since that time, they have been the heart and soul of several multibillion dollar industries, ranging from high-dielectric-constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves. Materials based on two compositional systems, barium titanate and lead zirconate titanate, have dominated the field throughout their history. The more recent developments in the field of ferroelectric ceramics, such as medical ultrasonic composites, high-displacement piezoelectric actuators (Moonies, RAINBOWS), photostrictors, and thin and thick films for piezoelectric and integrated-circuit applications have served to keep the industry young amidst its growing maturity. Various ceramic formulations, their form (bulk, films), fabrication, function (properties), and future are described in relation to their ferroelectric nature and specific areas of application.

Origin of ferroelectricity in perovskite oxides

Abstract: FERROELECTRIC materials are characterized by a switchable macroscopic polarization. Most technologically important ferroelectrics are oxides with a perovskite structure. The origin of their ferroelectric behaviour is unclear, however, and there is incomplete understanding of why similar, but chemically different, perovskites should display very different ferroelectric behaviour. The great sensitivity of ferroelectrics to chemistry, defects, electrical boundary conditions and pressure arises from a delicate balance between long-range Coulomb forces (which favour the ferroelectric state) and short-range repulsions (which favour the nonpolar cubic structure). To model the transition accurately, total-energy techniques are required which incorporate the effects of charge distortion and covalency. Here I report results of electronic-structure calculations on two classic examples of ferroelectric perovskites, BaTiO3 and PbTiO3, and demonstrate that hybridization between the titanium 3d states and the oxygen 2p states is essential for ferroelectricity. The different ferroelectric phase behaviour of the two materials is also clear: in PbTiO3, the lead and oxygen states hybridize, leading to a large strain that stabilizes the tetragonal phase, whereas in BaTiO3 the interaction between barium and oxygen is completely ionic, favouring a rhombohedral structure.

Ferroelectric materials and their applications

Abstract: 1. Introduction - Characteristics of ferroelectrics. 2. Methods for measuring physical properties of ferroelectric materials. 3. Perovskite-type ferroelectrics (Part I). 4. Perovskite-type ferroelectrics (Part II). 5. Lithium niobate and lithium tantalate. 6. Ferroelectric tungsten - bronze type niobate crystals. 7. KDP family, TGS family and other water-soluble ferroelectric crystals. 8. Other ferroelectric crystal materials. 9. Organic ferroelectric materials and piezoelectric composites.

Oxygen-vacancy-related low-frequency dielectric relaxation and electrical conduction in B i : S r T i O 3

Abstract: The temperature dependence of dielectric properties and electrical conduction of $({\mathrm{Sr}}_{1\ensuremath{-}1.5x}{\mathrm{Bi}}_{x}){\mathrm{TiO}}_{3} (0.0133l~xl~0.133)$ was measured from 10 to 800 K. Three sets of oxygen vacancies related dielectric peaks (peaks A, B, and $C)$ were observed. These peaks could be greatly suppressed or eliminated by annealing the samples in an oxidizing atmosphere, and enhanced or recreated by annealing in a reducing atmosphere. The results show that the Maxwell-Wagner polarization is not the main mechanism, and the Skanavi's model also cannot be directly applied. A tentative explanation was suggested. Peak A, observed in the temperature range of 100--350 K with the activation energy for dielectric relaxation ${E}_{\mathrm{relaxA}}=0.32--0.49$ eV, is attributed to the coupling effect of the conduction electrons with the motion of the off-centered Bi and Ti ions; the conduction carriers in this temperature range are from the first ionization of oxygen vacancies ${(V}_{o}).$ Peaks B and C are also discussed.