Ferroelectric materials 2013 (original) (raw)
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Applied Physics Letters, 2002
Dielectric spectra of ceramic samples of Ca 1Ϫx Pb x TiO 3 (0рxр0.4) solid solutions were studied at frequencies between 10 Hz and 1 MHz in a temperature range of 4.2-300 K. A ferroelectric phase transition was observed at xϭ0.3 with transformation to a relaxor type behavior at xϾ0.3. The transition temperature T c follows a linear dependence T c ϰ(xϪx c) with x c ϭ0.28 contrary to a square-root dependence T c ϰ(xϪx c) 1/2 predicted by the theory for incipient ferroelectrics. The critical concentration essentially exceeds the x c values for SrTiO 3 and KTaO 3 incipient ferroelectrics.
Journal of Applied Physics
With increasing industrial acceptance of Na 0.5 Bi 0.5 TiO 3 (NBT)-based lead-free piezoceramics, there is a need to develop insights into the way different factors influence the microstructural-structural-piezoelectric property correlations. In this work, we have examined the role of structural disorder on the piezoelectric response of the pre-MPB composition x = 0.03 of the well-known solid solution series (1-x) Na 0.5 Bi 0.5 TiO 3-(x)BaTiO 3. Using off-stoichiometry on the A-site as a tuning parameter to vary the structural disorder, which we characterize in terms of the fraction of the "cubiclike phase" or variation in the thermal parameter of the A-site cation, it is shown that the piezo response maximizes for the composition, which retains an optimum degree of disorder after poling. Our study confirms the important role of structural disorder in enhancing piezoelectric response in ferroelectric ceramics.
The effect of Pb2+ substitution on the quantum paraelectric behaviour of CaTiO3
Journal of Physics-condensed Matter, 2006
Results of low temperature dielectric measurements on the mixed (Ca_(1-x)Pb_(x))TiO_(3) system are presented to show that a dielectric anomaly appears for x \geq 0.10. The observed dielectric peak is shown to be due to a thermodynamic phase transition and not due to a relaxor or dipole glass type transition. Curie-Weiss fit to the dielectric constant gives negative Curie temperature which points towards an antiferroelectric transition. Arguments are advanced to propose that CaTiO3 may be an incipient antiferroelectric in which Pb^(2+) substitution stabilises the antiferroelectric phase.
CuO as a sintering additive for (Bi1/2Na1/2) TiO3BaTiO3(K0. 5Na0. 5) NbO3 lead-free piezoceramics
Journal of the …, 2011
CuO as a sintering additive was utilized to explore a low-temperature sintering of 0.92(Bi 1/2 Na 1/2 )TiO 3 -0.06BaTiO 3 -0.02(K 0.5 Na 0.5 )NbO 3 lead-free piezoceramic which has shown a promise for actuator applications due to its large strain. The sintering temperature guaranteeing the relative density of greater than 98% is drastically decreased with CuO addition, and saturates at a temperature as low as ∼930 • C when the addition level exceeds ca. 1 mol.%. Two distinguished features induced by the addition of CuO were noted. Firstly, the initially existing two-phase mixture gradually evolves into a rhombohedral single phase with an extremely small non-cubic distortion. Secondly, a liquid phase induced by the addition of CuO causes an abnormal grain growth, which can be attributed to the grain boundary reentrant edge mechanism. Based on these two observations, it is concluded that the added CuO not only forms a liquid phase but also diffuses into the lattice. In the meantime, temperature dependent permittivity measurements both on unpoled and poled samples suggest that the phase stability of the system is greatly influenced by the addition of CuO. Polarization and strain hysteresis measurements relate the changes in the phase stability closely to the stabilization of ferroelectric order, as exemplified by a significant increase in both the remanent strain and polarization values. Electron paramagnetic resonance (EPR) spectroscopic analysis revealed that the stabilization of ferroelectric order originates from a significant amount of Cu 2+ diffusing into the lattice on B-site. There, it acts as an acceptor and forms a defect dipole in association with a charge balancing oxygen vacancy.
Crystal growth and piezoelectricity of BaTiO[sub 3]–CaTiO[sub 3] solid solution
Applied Physics Letters, 2008
We report the crystal growth and piezoelectric properties of ͑1−x͒BaTiO 3 -xCaTiO 3 . It is found that the perovskite structure is facilitated by incorporating small Ca into Ba site and single crystals for a wide composition range of 0.02ഛ x ഛ 0.34 can be grown by the floating zone technique with a high rate of 20 mm/ h. High values of piezoelectric coefficient ͑d 33 = 180-310pC/ N͒ have been demonstrated for the single crystals as well as the biphasic polycrystals with composition close to the solid solution limit. These findings may stimulate further interests in the developments of lead-free piezoelectrics or optical devices.
Journal of Physics: Condensed Matter
Piezoelectric and other physical properties are significantly enhanced at (or near) a morphotropic phase boundary (MPB) in ferroelectrics. MPB materials have attracted significant attention owing to both fundamental physics as well as the possibility of wellregulated energy and information storage devices which are dominated by lead (Pb)-based materials. Here, we report the crystal structure, Raman spectra, dielectric constant and polarization near the MPB of lead free (1 − x) Na 0.5 Bi 0.5 TiO 3 − x BaTiO 3 (0.00 ⩽ x ⩽ 0.10) solid-solution, prepared by sol-gel auto combustion technique and sintered by microwave sintering technique. With the addition of BaTiO 3 into Na 0.5 Bi 0.5 TiO 3 , it induces a structural phase transition from R3c (a single phase) to R3c + P4mm (a dual phase) close to x = 0.06 and 0.07 and transform to a high symmetry tetragonal phase P4mm at higher compositions (x = 0.08 to 0.10) as evident from our x-ray Rietveld refinement and Raman spectroscopic results. We perform first-principles calculations based on density functional theory that confirm a structural transition from a rhombohedral to a tetragonal phase under increasing x. In the prepared solid solution, an anomalous enhancement of remnant polarization (2P 0 r) was observed for x = 0.06 and 0.07, which has been explained based on the existence of the MPB. On the other hand, the value of coercive field E 0 C was found to be decreased linearly from x = 0.00 to 0.06; it is constant for higher compositions. Further details of the ferroelectric properties on the electric field poled samples have been studied and compared with the as-grown (unpoled) samples.
Synthesis and Structural Study of Ferroelectric Material Lead Titanate (PbTiO3)
Journal of Mountain Research, 2021
Lead Titanate PbTiO3, (PT) is technologically important ferroelectric and piezoelectric ceramics. To make PbTiO3, the oxides PbO and TiO2 are combined in a stoichiometric ratio. Solid-state reaction process was used to synthesize the oxides. The calcination temperature was 8500C. The prepared sample has been characterized by XRD techniques with a scanning rate of 6 degree per minutes. The prepared sample PbTiO3 shows crystalline nature, with Tetragonal symmetry, as observed by X –ray measurements. A scanning electron microscope (SEM) was used to examine the surface morphology and grain size of the obtained samples. Micrographs obtained from SEM analysis revealed a single phase sample of well-defined grains.
Physical Review B, 2008
We report here an anomalous peak in the composition dependence of the dielectric permittivity of nonferroelectric ͑1−x͒NaNbO 3-xCaTiO 3 ceramics for the composition range 0.10Ͻ x Ͻ 0.20. This is reminiscent of a similar phenomenon in the ferroelectric morphotropic phase boundary ceramics. Rietveld analysis of the powder x-ray diffraction data for various compositions reveals that this peak is linked with a change of crystal structure from one orthorhombic phase in the Pbma space group for 0 ഛ x ഛ 0.10 to another orthorhombic phase in the Pbnm space group for x ജ 0.20 through an intermediate long period modulated orthorhombic phase whose lattice parameter is ϳ14 times the lattice parameter of the Pbnm phase of CaTiO 3 in the ͓010͔ direction ͑q ϳ͓0,1/ 14,0͔͒.
Journal of Asian Ceramic Societies, 2019
Dense Ba 1-x Pb x TiO 3 (x = 0-0.20) samples (>90% TD) were fabricated through a solid-state reaction route involving wet ball milling for 24 h and calcination at 1150°C for 4 h, followed by sintering at 1300°C for 4 h. XRD results for all the samples revealed a tetragonal perovskite (P4mm) crystal structure. Increased substitution of Pb caused monotonic growth in the tetragonality character of the perovskite phase. Although, the value of ε r ʹ dropped from an initial value of 3000 for x = 0 (pure BaTiO 3) to 400 for x = 0.20 samples, the losses (tanδ) interestingly declined almost to half. A substantial increase in the Curie temperature from 120°C for x = 0°C to 180°C for x = 0.15 samples was noted. P-E loop analysis revealed an increase in the saturation polarization by almost 1.5 times, moreover, in the remnant polarization by six times with Pb-substitution. The d 33 values demonstrated an increase from 95 pC/N for pure BaTiO 3 samples to 220 pC/N for x = 0.15 samples.
Journal of Electronic Materials, 2017
Crystal structure, dielectric, ferroelectric, piezoelectric, and electric field-induced strain properties of lead-free Nb-modified 0.96Bi 0.5 K 0.5 TiO 3-0.04Bi(Mg 0.5 Ti 0.5)O 3 (BKT-BMT) piezoelectric ceramics were investigated. Crystal structure analysis showed a gradual phase transition from tetragonal to pseudocubic phase with increasing Nb content. The optimal piezoelectric property of small-signal d 33 was enhanced up to 68 pC/N with a lower coercive field (E c) of 22 kV/cm and an improved remnant polarization (P r) of 13 lC/cm 2 for x = 0.020. A relaxor-like behavior with a frequency-dependent Curie temperature T m was observed, and a high T m around 320°C was obtained in the investigated system. This study suggests that the ferroelectric properties of BKT-BMT was significantly improved by means of Nb substitution. The possible shift of depolarization temperature T d toward high temperature T m may have triggered the spontaneous relaxor to ferroelectric phase transition with long-range ferroelectric order without any traces of a nonergodic relaxor state in contradiction with Bi 0.5 Na 0.5 TiO 3-based systems. The possible enhancement in ferroelectric and piezoelectric properties near the critical composition x = 0.020 may be attributed to the increased anharmonicity of lattice vibrations which may facilitate the observed phase transition from a low-symmetry tetragonal to a high-symmetry cubic phase with a decrease in the lattice anisotropy of an undoped sample. This highly flexible (at a unit cell level) narrow compositional range triggers the enhancement of d 33 and P r values.