Large electric field-induced strain and piezoelectric responses of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-Ba(Ti0.90Sn0.10)O3 ceramics near morphotropic phase boundary (original) (raw)
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Journal of Alloys and Compounds, 2011
In this study, lead-free 0.975[Bi 0.5 (Na 1−x K x ) 0.5 TiO 3 ]-0.025BiAlO 3 piezoelectric ceramics (BNKT-BA) with x ranging from 0 to 0.25 were fabricated using a conventional solid state reaction. The effects of potassium concentration (x) on the structure and electrical properties of the ceramics were investigated. The X-ray diffraction patterns revealed that the addition of K + improved the crystal symmetry of the BNKT-BA ceramics and produced a rhombohedral-tetragonal morphotropic phase boundary (MPB) in the range of 0.15 ≤ x ≤ 0.20. The increase of the K + concentration resulted in a decreased grain growth rate and promoted the formation of grains with a cubic shape. The BNKT-BA ceramics exhibited high remanent polarizations of 25 C/cm 2 near the rhombohedral side of the MPB composition (x = 0.15). The polarization and strain hysteresis loops demonstrated that an increased K + concentration (x ≥ 0.20) destabilized the ferroelectric order of the BNKT-BA ceramics, leading to degradation of the remanent polarization and coercive field. However, the destabilization of the ferroelectric order was accompanied by significant enhancements in the bipolar and unipolar strains. A large electric field-induced strain (S = 0.33%) and a corresponding normalized strain (d * 33 = S max /E max = 533 pm/V) were obtained on the tetragonal side of the MPB composition (x = 0.22).
Sensors and Actuators A: Physical, 2010
Lead-free Zr-modified Bi 0.5 (Na 0.78 K 0.22 ) 0.5 TiO 3 ceramics (BNKTZ-100x, with x = 0-0.05) were synthesized by a conventional ceramic fabrication process and its influence on crystal structure and electromechanical properties was investigated. The temperature-dependent dielectric peaks of the BNKTZ-100x ceramics broadened and ferroelectric polarizations decreased with increasing Zr concentration. The BNKTZ-3 ceramics showed an enhanced unipolar field-induced strain of 0.43%. The dynamic piezoelectric coefficient (d * 33 = S max /E max ) obtained for this composition was 614 pm/V, much higher than that of polycrystalline lead-free and hard Pb(Zr,Ti)O 3 ceramics. These results indicate that an appropriate amount of Zr substitution significantly enhances the field-induced strain level of BNKT ceramics and can be considered as one of promising candidate materials for lead-free electromechanical actuator applications.
Journal of the Korean Physical Society, 2010
Lead-free piezoelectric (1 -x)(Bi0.5(Na0.75K0.25)0.5TiO3)-xBiAlO3 (BNKT25-BA, 0 ≤ x ≤ 0.10) ceramics were synthesized using a conventional solid state reaction method. The incorporation of BA into the BNKT25 lattice was investigated by using X-ray diffraction (XRD), ferroelectric characterizations and electric-field-induced strain behavior. X-ray diffraction revealed a pure perovskite phase for x ≤ 0.050. A phase transformation from tetragonal to pseudocubic was observed at x = 0.050. The polarization hysteresis loops of the BNTK25-BA ceramics indicate that the addition of BA significantly disrupts the ferroelectric order of BNKT25 ceramics. The destabilization of the ferroelectric order is accompanied by an enhancement of the unipolar strain. In particular, a large electric-field-induced strain (S = 0.29%) and a normalized strain (d * 33 = Smax/Emax = 484 pm/V) were observed at x = 0.025, near the tetragonal-pseudocubic phase boundary. These results suggest that the BNKT25-BA system is a promising candidate for lead-free electromechanical applications.
Journal of Electroceramics, 2013
In this paper, lead-free (1-x)(Bi 0.5 Na 0.5 ) 0.94 Ba 0.06-TiO 3 -xBiAlO 3 (BNBT-BA, x00, 0.010, 0.015, 0.020, 0.025, and 0.030) piezoelectric ceramics were synthesized using a conventional solid-state reaction method. The effect of BiAlO 3 concentration on dielectric, ferroelectric and piezoelectric properties were investigated. The ferroelectric and piezoelectric properties of BNBT ceramics are significantly influenced by the presence of BA. In the composition range studied, X-ray diffraction revealed a perovskite phase with the coexistence of rhombohedral and tetragonal phases. The temperature dependence of dielectric properties showed that the depolarization temperature (T d ) shifted towards lower temperatures and that the degree of diffuseness of the phase transition around T d and T m became more obvious with increasing BiAlO 3 content. The remanent polarization increased with increasing BA, and reached a maximum value of 30 μC/cm 2 at x00.020. As a result, at x00.020, the piezoelectric constant (d 33 ) and the electromechanical coupling factor (k p ) of the ceramics attained maximum values of 188 pC/N and 34.4 %, respectively. These results indicate that BNBT-BA ceramics is a promising candidate for leadfree piezoelectric materials.
Materials (Basel, Switzerland), 2017
Research and development of lead-free piezoelectric materials are still the hottest topics in the field of piezoelectricity. One of the most promising lead-free family of compounds to replace lead zirconate-titanate for actuators is that of Bi0.50Na0.50TiO₃ (BNT) based solid solutions. The pseudo-binary (1 - x)Bi0.50Na0.50TiO₃-xBa1 - yCayTiO₃ system has been proposed for high temperature capacitors and not yet fully explored as piezoelectric material. In this work, the solid solution with x = 0.06 and y = 0.10 was obtained by two different synthesis routes: solid state and Pechini, aiming at using reduced temperatures, both in synthesis (<800 °C) and sintering (<1150 °C), while maintaining appropriated piezoelectric performance. Crystal structure, ceramic grain size, and morphology depend on the synthesis route and were analyzed by X-ray diffraction, together with scanning and transmission electron microscopy. The effects of processing and ceramic microstructure on the structu...
Japanese Journal of Applied Physics, 2012
In this study, the effects of Bi(Zn 0:5 Ti 0:5)O 3 (BZT) on the structure, dielectric, ferroelectric, and piezoelectric properties of morphotropic phase boundary Bi 0:5 (Na 0:82 K 0:18) 0:5 TiO 3 (BNKT18) piezoelectric ceramics were investigated. In the composition range studied, X-ray diffraction results revealed the coexistence of rhombohedral and tetragonal phases. It was found that BZT content decreased the depolarization temperature (T d) of BNKT18-BZT ceramics, and the degree of diffuseness of the phase transition became more obvious with increasing BZT content. The addition of a small amount of BZT improved the piezoelectric properties, with the maximum piezoelectric constant (d 33 ¼ 166 pC/N) and electromechanical coupling factor (k p ¼ 31:7%) obtained at x ¼ 0:03. However, at a high concentration of BZT, the remanent polarization and piezoelectric constant d 33 were drastically decreased, and a pronounced enhancement in electric field-induced strain was observed, with a peak of 0:27% at x ¼ 0:07, which corresponds to a normalized strain, S max =E max , of 385 pm/V.
Solid State Communications, 2010
Lead-free perovskite solid solutions of (1 − x)(Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 )-xBiAlO 3 (abbreviated as BNKT20-BA, x = 0.00, 0.025, 0.050, 0.075, 0.100) were synthesized by a conventional solid state reaction method. XRD patterns revealed that a pure perovskite phase was formed for x ≤ 0.050. A structural transition from the coexistence of rhombohedral and tetragonal to pseudocubic phase was observed at x = 0.050. Polarization and strain hysteresis loops indicate that the ferroelectric order is disrupted significantly with the addition of BA. The destabilization of the ferroelectric order is accompanied by an enhancement of bipolar and unipolar strain. A large electric field-induced strain (S = 0.30%) and a normalized strain (d * 33 = S max /E max = 391 pm/V) were obtained at x = 0.050. These results provide evidence for the relation between the structural transition from the coexistence of rhombohedral and tetragonal into pseudocubic and the large electric field-induced strain in BNKT20-BA perovskite solid solutions.
Current Applied Physics, 2010
Lead-free piezoelectric (1 À x)(Bi 0.5 (Na 0.78 K 0.22 ) 0.5 TiO 3 )-xBiAlO 3 (abbreviated BNKT22-BA, x = 0.00-0.100) ceramics were synthesized using a conventional sintering technique. The incorporation of BA into the BNKT22 lattice was investigated by X-ray diffraction (XRD), and the dielectric and ferroelectric characterizations and electric field-induced strain behavior. We found that the structural and electrical properties of BNKT22 ceramics are significantly influenced by the presence of BA content. X-ray diffraction revealed a pure perovskite phase for x 6 0.050. A phase transformation from tetragonal to pseudocubic was observed at x = 0.050. As BA content increased, the maximum dielectric constant continuously decreased, and the depolarization temperature (T d ) shifted towards lower temperatures. The polarization and strain hysteresis loops indicate that the addition of BA significantly disrupts the ferroelectric order. The destabilization of the ferroelectric order is accompanied by an enhancement of bipolar and unipolar strains. In particular, a very large electric field-induced strain (S = 0.35%) and a normalized strain (d à 33 = S max /E max = 592 pm/V) were observed at x = 0.030, near the tetragonal-pseudocubic phase boundary. These results suggested that the BNKT22-BA system is a promising candidate for high performance, lead-free electromechanical applications.
Current Applied Physics, 2010
Lead-free Bi 0.5 (Na 0.78 K 0.22 ) 0.5 TiO 3 (BNKT) piezoelectric ceramics were synthesized by the solegel technique. The effects of sintering temperatures on the crystal structure, microstructure, densification, dielectric, ferroelectric and electric field-induced strain behaviors of the BNKT ceramics were investigated. X-ray diffraction patterns exhibited a pure perovskite structure from 1075 to 1150 C. A scanning electron microscopy study revealed an increase in grain size with increasing sintering temperature. The density of the ceramics sintered at 1150 C reaches a maximum value of 5.55 g/cm 3 , which is 96% of the theoretical density. BNKT ceramics sintered at an optimum temperature of 1150 C exhibited a high remnant polarization of 18.5 mC/cm 2 , a high electric field-induced strain of 0.20% and dynamic piezoelectric coefficient d 33 * ¼ (S max /E max ) of 247 pm/V.