Dielectric and electrical studies of SrBi 2 Nb 1.9 V 0.1 O 9 ferroelectric ceramics
03 Nov 2009-pp 1-5
TL;DR: In this article, the effect of sintering temperature on structural, dielectric and electrical properties of vanadium substituted strontium bismuth niobate ferroelectric ceramics have been studied.
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.
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TL;DR: In this article, the authors describe the preparation and characterization of thin-film capacitors using ferroelectric materials from a large family of layered perovskite oxides, exemplified by SrBi2Ta2O9, SRBi2NbTaO9 and SrBi4Ta4O15.
Abstract: A SIGNIFICANT fraction of the computer memory industry is at present involved in the manufacture of non-volatile memory devices1—that is, devices which retain information when power is interrupted. For such applications (and also for volatile memories), the use of capacitors constructed from ferroelectric thin films has stimulated much interest1. In such structures, information is stored in the polarization state of the ferroelectric material itself, which should in principle lead to lower power requirements, faster access time and potentially lower cost1. But the use of ferroelectrics is not without problems; the memories constructed to date have generally suffered from poor retention of stored information and degradation of performance ('fatigue') with use1–3. Here we describe the preparation and characterization of thin-film capacitors using ferroelectric materials from a large family of layered perovskite oxides, exemplified by SrBi2Ta2O9, SrBi2NbTaO9 and SrBi4Ta4O15. The structural flexibility of these materials allows their properties to be tailored so that many of the problems associated with previous ferroelectric memories are avoided. In particular, our capacitors do not show significant fatigue after 1012 switching cycles, and they exhibit good retention characteristics and low leakage currents even with films less than 100 nm thick.
2,378 citations
"Dielectric and electrical studies o..." refers background in this paper
...SrBi2Nb2O9 have attracted the attention of the researchers in recent years due to its large remanent polarization, low coercive field, low leakage current, high Curie temperature, lower sintering temperature and being lead free [1-5]....
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TL;DR: In this article, the spontaneous polarization of ferroelectric Bi4Ti3O12 was shown to be monoclinic point group m at 25°C, where m is the number of points in the a−c plane.
Abstract: The symmetry of ferroelectric Bi4Ti3O12 is shown to be monoclinic point group m. The spontaneous polarization PS is approx 50 μC/cm2 at 25°C and lies in the monoclinic a‐c plane at an angle of less than 5 deg from the plane of the crystal sheets. A complete determination of the optical indicatrix as a function of temperature is given. Switching for fields along the c axis occurs by a unique ``rocking'' of the large PS vector and leads to interesting electrical‐optical behavior. The domain structure is quite complex, and observed wall orientations are compared with those predicted theoretically.
760 citations
"Dielectric and electrical studies o..." refers background in this paper
...SrBi2Nb2O9 have attracted the attention of the researchers in recent years due to its large remanent polarization, low coercive field, low leakage current, high Curie temperature, lower sintering temperature and being lead free [1-5]....
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TL;DR: A high-temperature x-ray study revealed a symmetry change to tetragonal at 675\ifmmode^\circ\else\textdegree\fi{}C. The symmetry is orthorhombic with $a=5.411$ A, $c=32.83$ C, and $b=1.007$ C as mentioned in this paper.
Abstract: On the basis of dielectric studies on polycrystalline specimens, ${\mathrm{Bi}}_{4}$${\mathrm{Ti}}_{3}$${\mathrm{O}}_{12}$ has been established as a ferroelectric with a Curie temperature of 675\ifmmode^\circ\else\textdegree\fi{}C. The symmetry is orthorhombic with $a=5.411$ A, $c=32.83$ A, and $\frac{b}{a}=1.007$ at 25\ifmmode^\circ\else\textdegree\fi{}C. A high-temperature x-ray study revealed a symmetry change to tetragonal at 675\ifmmode^\circ\else\textdegree\fi{}C. The polar axis is probably the orthorhombic $b$ axis. ${\mathrm{Bi}}_{4}$${\mathrm{Ti}}_{3}$${\mathrm{O}}_{12}$ is a member of oxides with the general formula ${({\mathrm{Bi}}_{2}{\mathrm{O}}_{2})}^{2+}{({\mathrm{Me}}_{x\ensuremath{-}1}{R}_{x}{\mathrm{O}}_{3x+1})}^{2\ensuremath{-}}$. According to Aurivillius, the crystal structure of ${\mathrm{Bi}}_{4}$${\mathrm{Ti}}_{3}$${\mathrm{O}}_{12}$ comprises a stacking of ${\mathrm{Bi}}_{2}$${\mathrm{O}}_{2}$ and perovskite-like ${\mathrm{Bi}}_{2}$${\mathrm{Ti}}_{3}$${\mathrm{O}}_{10}$ layers along the pseudotetragonal $c$ axis. Multiple ion substitutions of (${\mathrm{Bi}}^{3+}$${\mathrm{Ti}}^{4+}$) in ${({\mathrm{Bi}}_{2}{\mathrm{O}}_{2})}^{2+}$${({\mathrm{Bi}}_{2}{\mathrm{Ti}}_{3}{\mathrm{O}}_{10})}^{2\ensuremath{-}}$ by (${\mathrm{Me}}^{2+}{\mathrm{Nb}}^{5+}$) where ${\mathrm{Me}}^{2+}=\mathrm{B}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{P}\mathrm{b},\phantom{\rule{0ex}{0ex}}\mathrm{o}\mathrm{r}\phantom{\rule{0ex}{0ex}}\mathrm{S}\mathrm{r}$ lead to a steep decrease of the Curie temperature.
281 citations
TL;DR: In this article, a systematic study of doping effects on the crystal structure, microstructure, dielectric, and electrical properties of layer-structured strontium bismuth niobate, SrBi2Nb2O9 (SBN), ferroelectrics was performed.
Abstract: This article reports a systematic study of doping effects on the crystal structure, microstructure, dielectric, and electrical properties of layer-structured strontium bismuth niobate, SrBi2Nb2O9 (SBN), ferroelectrics. Substitution in both the A site (Sr2+ by Ca2+ and Ba2+) and B site (Nb5+ by V5+) up to 30 at % were studied. It was found that crystal lattice constant, dielectric, and electrical properties of SBN ferroelectrics varied appreciably with the type and amount of dopants. The relationships among the ionic radii, structural constraint imposed by [Bi2O2]2+ interlayers, and properties were discussed.
142 citations
TL;DR: In this paper, the ferroelectricity of this Aurivillius type structure has been studied and it has been shown that the polarization disappears at temperatures between the two maxima of the dielectric constant.
Abstract: Ceramics based on the composition Bi2SrNb2O9 with isomorphic substitutions of cations in the Bi2O22+ and the perovskite layers, Bi2−xTexSr1−xNa(K)xNb2O9, have been prepared by solid state reaction. The ferroelectricity of this Aurivillius type structure has been studied. Dielectric measurements as a function of the temperature show a low temperature maximum in the dielectric constant that would correspond to a ferro-;paraelectric phase transition. The temperature of this maximum increases when the radius of the ion that substitutes Sr for decreases. A second maximum in the dielectric constant is found at higher temperature possibly corresponding to a relaxor ferroelectric. Measurements of remanent polarization as a function of the temperature seem to confirm the relaxor behavior, because the polarization disappears at temperatures between the two maxima of the dielectric constant. Saturated hysteresis loops are obtained for all the substituted samples at temperatures above 300 °C. Ferroelectric parameters such as the polarization, coercive field, and coupling factors of the BSN family compounds were obtained for the first time. The ac electric conductivity shows anomalies at temperatures close to those where the remanent polarization disappears. Activation energies calculated from measurements of dc electric conductivity, impedance arcs, and dielectric modulus data may be associated with thermally activated oxygen vacancies.
93 citations
"Dielectric and electrical studies o..." refers background in this paper
...This makes SrBi2Nb2O9 a potential material for FeRAM applications [ 6-10 ]....
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