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1.
Lead-free piezoelectric ceramics (1 − x)Bi0.5Na0.5TiO3xBaNb2O6 (BNT–BN100x), a new member of the BNT-based group, was prepared by conventional solid state reaction. X-ray diffraction showed that BaNb2O6 (BN) diffused into the lattice of Bi0.5Na0.5TiO3 to form a solid solution with perovskite-type structure. The temperature dependence of dielectric constant εr revealed that the solid solution underwent two phase transitions from ferroelectric to anti-ferroelectric and anti-ferroelectric to paraelectric. Both the transition temperature T d and T m were shifted to lower with the increasing content of BaNb2O6. The temperature dependence of dielectric constant at different frequency revealed that the solid solution exhibited obviously dielectric relaxation characteristics. The sample with x = 0.6 mol% exhibited excellent electrical properties, piezoelectric constant d 33 = 94 pC/N; electromechanical coupling factor k p = 0.185. The results showed that BNT–BN100x ceramics were good candidates for use as lead-free piezoelectric ceramics.  相似文献   

2.
Electrophoretic deposition (EPD) process has certain advantages such as it can be applied for a mass production and also can be combined with magnetic crystal alignment technique. In this work, we prepared lead-free 85(Bi0.5Na0.5)TiO3–15BaTiO3 (85BNT–15BT) piezoelectric ceramics by conventional uniaxial pressing and EPD process. Various conditions were optimized such as suspension media, applied electrical field, and deposition time in order to yield dense green ceramics of 85BNT–15BT composition using EPD process. 85BNT–15BT ceramics prepared using EPD process revealed the Curie temperature of about 250 °C, coercive field of about 30 kV/cm, and piezoelectric constant (d 33) of 75 pC/N. The EPD-processed samples exhibited structural and electrical properties similar to that of the conventionally processed one suggesting the successful fabrication of 85BNT–15BT piezoelectric ceramics by EPD method without composition deviation. This study lays a foundation on the fabrication of Bi-based lead-free piezoelectric ceramics by an alternative route other than the conventionally practiced solid-state reaction method maintaining the similar chemical composition, moreover, leaving a large space to explore more in the future.  相似文献   

3.
Two-step pressureless sintering of sol–gel derived 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 (BNT-BT) lead-free piezoelectric ceramics were investigated in comparison with conventional sintering. The effect of sintering regimes on the densification, grain growth behavior and electrical properties was discussed in detail. The results indicated that BNT-BT ceramics with a density of 95%, a relatively fine grain size of 850 nm and comparable piezoelectric properties (d33 ~170 pC/N, kp ~0.26, Qm ~102) had been achieved by pre-sintering at 1,150 °C to reach a critical density of 78%, and then cooling to a lower temperature of 1,050 °C for 20 h. The critical density value proves important at which the grain boundary diffusion could be maintained but the grain boundary migration suppressed at the same time. Moreover, the volatilization loss of Bi and Na elements could be inhibited by two-step sintering. Both the reduction of the grain size and the inhibition of the stoichiometry deviation together account for the variation of various electrical properties.  相似文献   

4.
PVDF-modified 0–3 connectivity cement-based/lead-free 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 piezoelectric ceramic composites were fabricated using 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 (BNBT), Portland cement, and polyvinylidene fluoride (PVDF). The microstructure, acoustic impedance (Z c), dielectric properties, and influence of poling temperature and electrical poling field on the piezoelectric coefficient (d 33) and the total period of the poling process of composites with 50 vol% BNBT and 1–10 vol% PVDF were investigated. The results indicated that Z c, the dielectric constant, and the dielectric loss of the composites decrease as the PVDF content increases. The d 33 of the composites was found to enhance more clearly when the content of PVDF is more than 2 vol%. The d 33 results of the composites showed an optimum increase of 45% when 5 vol% PVDF was used (under an electrical poling field of 1.5 kV/mm and a poling temperature of 80°C). Moreover, these composites with PVDF were found to exhibit enhanced poling behavior in that the PVDF was able to reduce the total period of the poling process. Interestingly, the piezoelectric voltage coefficient (g 33) of the composite with 5 vol% PVDF content had the highest value of 33.59 mV·m/N. Therefore, it can be safely concluded that this new kind of PVDF-modified 0–3 connectivity cement-based/lead-free 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 piezoelectric ceramic composite has the potential to be used in concrete as a sensor for structural health monitoring applications.  相似文献   

5.
New lead-free ceramics (1–x)NaNbO3–xBi0.5K0.5TiO3 have been fabricated by the conventional ceramic sintering technique, and their ferroelectric and piezoelectric properties have been studied. The results of X-ray diffraction reveal that Bi0.5K0.5TiO3 diffuses into the NaNbO3 lattices to form a new perovskite-type solid solution with orthorhombic symmetry. The addition of a small amount of Bi0.5K0.5TiO3 (x ≥ 0.025) transforms the ceramics from antiferroelectric to ferroelectric. The ceramic with x = 0.10 possesses the largest remanent polarization P r and thus exhibits the optimum piezoelectric properties, giving d 33 = 71 pC/N, k p = 16.6% and k t = 39.7%. The ceramics with low doping level of Bi0.5K0.5TiO3 are normal ferroelectrics and the ferroelectric-paraelectric phase transition becomes diffusive gradually with the doping level x of Bi0.5K0.5TiO3 increasing. Our results show the (1–x)NaNbO3–xBi0.5K0.5TiO3 ceramics is one of the good candidates for lead-free piezoelectric and ferroelectric materials.  相似文献   

6.
The (100) oriented and random oriented 0.755Bi0.5Na0.5TiO3–0.065BaTiO3–0.18SrTiO3 (BNT–BT–ST) thin films were deposited on LaNiO3 (LNO) buffered Pt(111)/Ti/SiO2/Si substrates by the sol–gel processing technique. The orientation is controlled by the concentration of solution. The structure, dielectric and piezoelectric properties of the thin films are significantly affected by the crystallographic orientation. The (100) oriented BNT–BT–ST thin film has improved dielectric and piezoelectric properties. For the (100) oriented and random oriented BNT–BT–ST thin films, the dielectric constants are 660 and 550, the dielectric losses are 0.045 and 0.076 and the effective piezoelectric coefficients are 140 and 110 pm/V, respectively. The large piezoelectric response is attributed to the uniform microstructure and increased lattice distortion along (100) direction.  相似文献   

7.
Lead-free ceramics (1???x)Bi0.5Na0.5TiO3xSr0.85Bi0.1TiO3 (BNT–xSBT, x?=?0.4, 0.5, 0.6 and 0.7) were prepared by a solid-state reaction process. Coexistence of ferroelectric relaxation at low temperature and Maxwell–Wagner dielectric relaxation at high temperature was revealed for the first time in this system. Meanwhile, hysteresis-free PE loops combined with a very high piezoelectric strain coefficient (d33) of 1658 pC/N concurrently with large electrostrictive coefficient Q?=?0.287 m4C?2 were achieved. The ferroelectric relaxor behavior and large electrostrictive strain might be linked to easy reorientation and reversal of ergodic PNRs and the combined effect of Bi off-center position and lone pair electrons.  相似文献   

8.
(1 − x)BaTiO3x(Bi0.5Na0.5)TiO3 (x ranged from 0.01 to 0.96) ceramics were fabricated by the conventional ceramic technique. The crystal structure, as well as dielectric and piezoelectric properties of the ceramics were studied. All the ceramics formed single-phase solid solutions with perovskite structure after sintering in air at 1150–1250 °C for 2–4 h. The crystal structure and microstructure varied gradually with the increase of (Bi0.5Na0.5)TiO3 (BNT) content. The Curie temperature, T c, shifted monotonously to high temperature as BNT increased. The ceramics with 20–90 mol% BNT had relatively low and stable dielectric loss characteristics. The piezoelectric constant, d 33, enhanced with the increase of BNT content through a maximum value in a composition of 93 mol% BNT and then tended to decrease. The maximum value, 148 pC/N, of piezoelectric constant d 33 together with the electromechanical coupling factors, k t, 19.8% and k p, 15.8%, were obtained when BNT was 93 mol%.  相似文献   

9.
The (1−x)Bi0·5(Na0·82K0·18)0·5TiO3−x LiSbO3 (x = 0−0·03) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method and the effect of LiSbO3 addition on microstructure and electrical properties of the ceramics was investigated. The results of XRD measurement show that Li+ and Sb5+ diffuse into the Bi0·5(Na0·82K0·18)0·5TiO3 lattices to form a solid solution with a pure perovskite structure. The LiSbO3 addition has no remarkable effect on the crystal structure. However, a significant change in grain size took place. Simultaneously, with increasing amount of LiSbO3, the temperature for a antiferroelectric to paraelectric phase transition clearly increases. The piezoelectric constant d 33 and the electromechanical coupling factor k p show an obvious improvement by adding small amount of LiSbO3, which shows optimum values of d 33 = 175 pC/N and k p = 0·36 at x = 0·01.  相似文献   

10.
3MgO–Al2O3–3TiO2 (MAT) ceramics were prepared by a conventional solid-state reaction method. The crystal structure, sintering behavior and microwave dielectric properties of ceramics were investigated using X-ray diffraction, scanning electron microscopy and network analyzer. MAT ceramics contained the coexistence of three phases, including MgAl2O4, MgTiO3 and MgTi2O5. The ceramics sintered at 1350 °C for 4 h presented excellent comprehensive performances with relative permittivity (ε r ) of 15.4, quality factor (Q × f) of 91,000 GHz and temperature coefficient of resonant frequency (τ f ) about ?55.1 ppm/°C.  相似文献   

11.
Donor-doped lead-free Bi0.7Ba0.3(Fe0.7Ti0.3)1?x Nb0.66x O3 + 1 mol% MnO2 ceramics were prepared by a conventional oxide-mixed method and the effects of Nb-doping on microstructure, piezoelectric and ferroelectric properties of the ceramics were investigated. All the ceramics exhibit a pure perovskite structure with rhombohedral symmetry. The grain growth of the ceramics is inhibited after the addition of Nb doping. High electric insulation (R = 109–1010 Ω?cm) and the poor piezoelectric performance and weak ferroelectricity are observed after the addition of Nb2O5 in the ceramics. Different from the donor effect of Pb-based perovskite ceramics, the introduction of Nb into 0.7BiFeO3–0.3BaTiO3 degrades the piezoelectricity and ferroelectricity of the ceramics. The Bi0.7Ba0.3(Fe0.7Ti0.3)1?x Nb0.66x O3 + 1 mol% MnO2 ceramic with x = 0 exhibits the optimum piezoelectric properties with d 33 = 133 pN C?1 and k p = 0.29 and high Curie temperature (TC = 603°C).  相似文献   

12.
In this study, NaNO3, Bi(NO3)3·5H2O, Ba(NO3)2, Ti(OC4H9)4 and citric acid were successfully introduced to fabricate lead-free piezoelectric (Na0.5Bi0.5)0.94Ba0.06TiO3 [NBBT] nanopartical powders by a novel modified sol–gel auto-combustion method. The resultant products were characterized by the X-ray diffraction analysis and transmission electron microscope method. (Na0.5Bi0.5)0.94Ba0.06TiO3 + Mn(NO3)2 [NBBTM] can be sintered by the traditional solid-state reaction, and the effects of NBBT doped different amounts of Mn(NO3)2 at various sintering temperatures upon phase formation, microstructure as well as piezoelectric properties were further studied. The experimental results show that it was helpful to control their chemical ingredients and microstructure to prepare nanocrystalline single phase NBBT powders. Where is the X-ray diffraction result of the corresponding ceramics to prove the existence of the mixing between rhombohedral and tetragonal phases at the MPB compositions. Doping 0.015 mol% Mn(NO3)2 into NBBT at 1,090 °C, piezoelectric constant (d 33) and relative dielectric constant (εr) reach the superior value of 159pC/N and 1,304, respectively, and dielectric loss (tan δ) and electromechanical coupling factor (K t) are 2.5% and 65%, respectively.  相似文献   

13.
The influences of Bi substitution on microwave dielectric properties of Ba4(La0.5Sm0.5)9.33Ti18O54 solid solutions were investigated. Dielectric ceramics with general formula Ba4(La(0.5−z)Sm0.5Bi z )9.33Ti18O54, z = 0.0–0.2 were prepared by conventional solid state route. The structural analysis of all the samples was carried out by X-ray diffraction and scanning electron microscopy. The dielectric properties were investigated as a function of Bi contents using open-ended coaxial probe method in the frequency range 0.3–3.0 GHz at room temperature. Dielectric constant varies from 83 to 88 and loss tangent from 2.1 × 10−3 to 5.5 × 10−3 at 3 GHz with temperature coefficient of resonant frequency changing from 106.7 to −8.4 ppm/oC as Bi contents increases from z = 0.00–0.20. It has been found that dielectric constant and temperature coefficient of resonant frequency improve whereas loss tangent is adversely affected with increase in Bi substitution.  相似文献   

14.
The lead free ceramics of two different stoichiometric 0.9(Bi0.5Na0.5)TiO3-0.1Ba(Ti1−x Zr x )O3 (abbreviated as BNBTZ-100x, x = 0, 0.045, 0.050, 0.055, 0.060) and 0.9(Bi0.5Na0.5−y Li y )TiO3-0.1Ba(Ti0.945Zr0.055)O3 (abbreviated as BNLBTZ-100y, y = 0, 0.015, 0.025, 0.035, 0.05, 0.075, 0.10, 0.125) compositions were prepared by the conventional ceramic fabrication technique. The crystal structure, dielectric and piezoelectric properties of the ceramics were investigated. All the ceramics formed single-phase solid solutions with tetragonal pervoskite structure, which was affected obviously by the addition of Zr and Li. The T m of the BNBZT-100x ceramics trends to increase whereas the T d trends to decrease as Zr content increases. And the T d of the BNLBZT-100y increases from 107 to 157 °C when y increases from 0 to 0.015, but decreases sharply as y increases further. The d 33 and k p of the BNBTZ-100x ceramics tend to increase with the addition of Zr. The maximum values of d 33 and k p, 156 pC/N and 18.9%, are obtained when x = 0.055. The d 33 of the BNLBTZ-100y ceramics keep almost unchanged when y increases from 0 to 0.035. And maximum value of k p, 16.3%, of the BNLBTZ-100y ceramics is obtained when y = 0.015.  相似文献   

15.
xSr0.7Ce0.2TiO3–(1???x)Sr(Mg1/3Nb2/3)O3 ceramics, referred to xSCT–(1???x)SMN, were successfully produced by conventional solid-state sintered technology. The compounds, belonging to perovskites with a secondary phase of CeO2, can be detected even with x down to 0.1 of SCT composition. The overall trend for grain growth illustrates the increase with increasing SCT doping level. The Raman peak at 825 cm?1 splits into two peaks and causes red shift phenomenon. XPS spectra indicate that Ti and Nb ions exist respectively in tetravalence and pentavalence, and Ce ions exist in trivalence and tetravalence. Dielectrics constant (ε r ) of SCT–SMN ceramics gradually increases with increasing theoretical dielectric polarizabilities. A wider width of the 825 cm?1 for FWHM of A1g mode Raman peaks suggests to a lower Q?×?f value. The increasing tolerance factor in agreement with temperature coefficient of resonant frequency (τ f ), denotes that the rise of perovskite symmetry. The 0.1SCT–0.9SMN ceramic sintered at 1450?°C for 4 h illustrates excellent microwave dielectric properties with ε r ?~?35.4, Q?×?f?~?11282 GHz and τ f ?~?1.7 ppm/°C. Activation energies of 0.1SCT–0.9SMN ceramic at 100, 300 and 500 V, are ~0.436, 0.427 and 0.331 eV, respectively, indicative of a decreased trend with external electric field.  相似文献   

16.
The properties of the composite, having a complicated microstructure, are decided by many factors such as those of glass matrix, crystal phases, fillers, and holes. We investigated how the addition of ceramic fillers to the glass matrix affects the mechanical and etching properties of the glass composite by forming new crystal phases. Different amounts of two fillers, ZnO and Al2O3, were added to a glass frit consisting of Bi2O3–ZnO–B2O3. It was sintered at 550 °C for 30 min. Based on the results of this study, the porosity and degree of crystallization of the composites could be controlled by adjusting the content of the ZnO and Al2O3 fillers. Therefore, porosity and degree of crystallization formed by the reaction between a glass matrix and fillers influence the mechanical and etching properties of the composite.  相似文献   

17.
Polycrystalline lead-free (Na0.46Bi0.46Ba0.08)(MnxTi1?xO3)?+?0.2CuO ceramics (x?=?0.0, 0.5, 2.0, 3.0 wt%) were prepared via solid-state reaction method. X-ray diffraction (XRD) analysis confirmed the formation of single-phase perovskite structure and indicated the presence of morphotropic phase boundary, where the tetragonal and rhombohedral phases co-existed for all the synthesized compositions. Scanning electron microscopy (SEM) analysis revealed that the average grain size decreased with the increase in Mn content. Impedance spectroscopy (IS) indicated that Mn doping was found to decrease the grain boundary resistance. Two semi-circles were observed for higher Mn content which indicates the contribution of both bulk grains and grain boundaries. Non-Debye type and temperature dependent relaxation phenomenon was also revealed by IS studies. The activation energies at different frequencies were found to be 0.05–0.9 eV, indicating hopping charge conduction mechanism. These results have comprehensive implications for the expanded use of BNT based lead free piezoelectric ceramics for practical applications.  相似文献   

18.
CaO–SrO–Li2O–Ln2O3–TiO2 ceramics were prepared by solid state reaction method, where Ln2O3 consists of equal proportions of Nd2O3 and Sm2O3. Dielectric properties and crystal structure were investigated with respect to the content of TiO2. Single phase with an orthorhombic perovskites structure was formed within the composition range of investigation. The frequency dependence of dielectric properties of the present ceramics was extensively investigated. Dielectric constant was less sensitive to frequency. However, dielectric loss and temperature coefficients were both very sensitive to frequency and gradually decreased with increasing frequency, such as the variation was more than ten times between 1 MHz and several GHz. The relationship between the temperature coefficient and dielectric loss was also discussed at different frequencies. And the mechanism of the frequency dependence was discussed in term of the role of Li ions.  相似文献   

19.
Ho3+-modified Pb(Zn1/3Nb2/3)O3–9PbTiO3 (PZN–9PT) single crystals were grown through a flux method. Phase structure and microstructural morphology of the as-grown single crystals were performed by X-ray diffraction analysis and scanning electron microscopy. The refinement of the lattice parameters were obtained by the Rietveld method. The electrical properties of PZN–9PT single crystals were improved significantly by the modification of Ho3+ ions. The rhombohedral–tetragonal phase transition temperature, Curie temperature, coercive field at 15 kV cm?1, and remnant polarization of Ho3+-modified PZN–9PT single crystals were increased by 14, 42 K, 2.4 kV cm?1, and 7.5 μC cm?2, respectively (i.e., 375.45, 448.45 K, 5.9 kV cm?1, and 38.40 μC cm?2, respectively). Furthermore, Lorentz-type law was used to describe the dielectric relaxor behavior of the as-grown single crystals.  相似文献   

20.
The purpose of this work is to study the optical properties and crystallization of glasses in the ternary system Bi2O3–MoO3–B2O3. In order to verify the obtaining of bismuth borate crystal phases several glass compositions have been selected for crystallization. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy and UV–Vis spectroscopy. The UV–Vis spectroscopy showed that the obtained glasses are transparent in the visible region. The values of optical band gap (E opt) and changes in cut-off (λc) depending on composition are reported. It was established that the increase in the MoO3 content led to decreasing the transmittance of the glasses. Moreover, the absorption edge shifts towards longer wavelength.  相似文献   

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