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ABSTRACT: To improve both the temperature stability and the mechanical quality factor of (K0.5Na0.5)0.94Li0.06NbO3 (KNLN6) ceramics, dense (K4CuNb8O23, Bi2O3)-modified KNLN6 lead-free ceramics were prepared. Results showed that the (K4CuNb8O23, Bi2O3)-modified ceramics exhibited a flat, temperature-stable behavior over the range of 20–120°C. K4CuNb8O23 (KCN) and Bi2O3-codoping changed the KNLN6 to “hard” ceramics with a significant improvement of mechanical quality factor, Q
m, from 82 to 756. Meanwhile, the piezoelectric constant, d
33, and the planar electromechanical coefficient, k
p, still maintained relatively high levels (d
33 ~118pC/N, k
p ~35.6%). These results indicate that the modified KNLN6 ceramics are promising lead-free piezoelectric candidates for practical
applications.
Journal of Materials Science 05/2012; 44(22):6162-6166. · 2.02 Impact Factor
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ABSTRACT: We report on excellent temperature stability of the Dy-doped (Ba0.99Ca0.01)(Ti0.98Zr0.02)O3 (BCZT-D) ceramics with high piezoelectric coefficient of d33 = 366 pC/N and planar electromechanical coupling factor of kp = 43.0%. Meanwhile, Curie temperature of the BCZT-D ceramics is found to be 125°C. Greatly improved temperature stability of the electromechanical coupling coefficients is found over a common usage temperature range between 20°C and 100°C, in which the BCZT-D ceramics exhibit pure tetragonal phase. The results indicate that the BCZT-D ceramics are promising lead-free materials for practical applications.
Journal of the American Ceramic Society 07/2011; 94(10):3181 - 3183. · 2.27 Impact Factor
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ABSTRACT: Lead-free (Ba1−xCax)(Ti0.95Zr0.05)O3 (x=0.02–0.20) ceramics were prepared successfully using a solid-state reaction technique. The polymorphic phase transitions from orthorhombic to tetragonal phase around room temperature were identified in the composition range of 0.06<x<0.10. A high piezoelectric coefficient of d33=365 pC/N and high planar electromechanical coupling factor of kp=48.5% were obtained for the sample of x=0.08. With the doping of Ca content, the orthorhombic–tetragonal phase transition point shifted toward room temperature while the relative high Curie temperature (Tc) was still maintained about 110°C.
Journal of the American Ceramic Society 07/2010; 93(10):2942 - 2944. · 2.27 Impact Factor
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ABSTRACT: SrBi4Ti4O15(SBTi) powders were synthesized by a novel hybrid method of sol–gel and ultrasonic atomization. TiO2 particle was used as a starting material to replace other expensive soluble titanium salts. X-ray diffraction results showed that the pure-phase SBTi powders were obtained at 700°C for 2 h, which is much lower than the calcination temperature (800°–850°C) required in solid-state reactions. The ceramics sintered at 1100°C for 1 h exhibited 94.5% of relative density and a piezoelectric coefficient of 21 pC/N. The results showed that this hybrid method could lead to an attractive method for the industrial fabrication of SBTi materials.
Journal of the American Ceramic Society 02/2008; 91(3):910 - 913. · 2.27 Impact Factor
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ABSTRACT: The effects of a small amount MnO2 (0–1.20 mol%) doping on the phase transition behavior, microstructure and electrical properties of (K0.5Na0.5)0.94Li0.06NbO3 (KNLN6) ceramics have been investigated. X-ray diffraction analysis showed that the ceramics underwent a perovskite structure transition from tetragonal to orthorhombic symmetry with increasing the MnO2 content, which is similar to the morphtropic phase boundary (MPB). SEM and density studies revealed that a small amount of MnO2 improved effectively the densification of the KNLN6 ceramics. Because of the high densification, the mechanical quality factor Qm of the KNLN6 ceramics were significantly enhanced by MnO2 addition which meant MnO2-doping changed the KNLN6 to “hard” ceramics. For 1.20 mol% MnO2-doped KNLN6 ceramics, the mechanical quality factor Qm reached up to 301, which increased by four times as compared with KNLN6. The piezoelectric constant d33 and the planar electromechanical coefficient kp still maintained relatively high levels, which were about 141 pC/N and 32.0%, respectively.
Materials Chemistry and Physics 118(1):229-233. · 2.23 Impact Factor
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ABSTRACT: Lead-free relaxor ceramics with composition (Na0.5K0.5)1−3xLaxNb0.95Ta0.05O3 (KNTN-Lax) were prepared by the conventional solid-state route. The ferroelectric relaxor behavior and dielectric properties of KNTN-Lax ceramics were systemically investigated. X-ray diffraction analysis showed that the crystal structure of the ceramics changed from orthorhombic to pseudo-cubic with increasing La-doping level. Dielectric study revealed that KNTN-Lax ceramics underwent a transition from a normal ferroelectric to relaxor-like ferroelectric. Furthermore, P–E hysteresis loops, which were of slim-loop type with small remnant polarization values in the composition range of 0.015 ≤ x ≤ 0.03 confirmed the ferroelectric relaxor behavior of KNTN-Lax ceramics. The samples of KNTN-Lax ceramics in the composition range from x = 0 to 0.015 exhibited good electrical properties, piezoelectric constant d33 of 98–119 pC/N and electromechanical coupling coefficients kp of 33.2–37.0%, respectively. The results show that the series of KNTN-Lax ceramics is one of the promising lead-free materials for electromechanical transducer applications.
Journal of Alloys and Compounds 484:233-238. · 2.29 Impact Factor
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ABSTRACT: Lead-free (K0.5Na0.5)0.96Sr0.02Nb(1−x)SbxO3 ceramics have been synthesized by using conventional ceramics technique. The structural variation and dielectric behavior of (K0.5Na0.5)0.96Sr0.02Nb(1−x)SbxO3 ceramics were systemically investigated. X-ray diffraction analysis showed that a morphotropic phase boundary between orthorhombic and tetragonal phases existed in the composition range of 0.04<x<0.06. Dielectric study revealed that the dielectric relaxor behavior was induced by doping Sr and Sb into (Na0.5K0.5)NbO3 and a typical dielectric relaxor behavior (the limiting value γ=1.900) was obtained at x=0.05, where the morphotropic phase boundary existed. The samples in the composition range from x=0.01 to 0.05 exhibited good electrical properties, piezoelectric constant d33 of 101–109 pC/N and electromechanical coupling factor kp of 34.1–35.4%, respectively. The results showed that the ceramics are one of the promising lead-free materials for electromechanical transducer applications.
Physica B Condensed Matter 404:1974-1978. · 1.06 Impact Factor
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ABSTRACT: Layer-structured Bi4Ti3−xNbxO12+x/2 (BiTN) ceramics, where x = 0.02–0.20, have been prepared by the conventional sintering technique. XRD results reveal the existence of an orthorhombic structure. The grain size decreases gradually and grain growth anisotropy is limited when x increases. The domain structures of BiTN ceramics differ on x. Nb5+ donor doping decreases markedly electrical conductivity of the materials and Tc shifts gradually to lower temperatures. In addition, low dielectric losses and good temperature stability of dielectric constant are obtained in a wide temperature range. Ferroelectric hysteresis loops of the materials are also determined on x. The best properties can be found in x = 0.08 and 0.11, indicating lower electrical conductivity, good temperature stability of dielectric properties and adequate piezoelectric properties.
Materials Science and Engineering: B.
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ABSTRACT: By adding excess of Na2CO3 as sintering aid, Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 (BNKLT-Nax) composition ceramics were fabricated at sintering temperature as low as 1000 °C using conventional solid phase synthesis method. The dielectric and piezoelectric properties of ceramics were investigated with the amount of different Na2CO3 substitutions. At the sintering temperature of 1020 °C, Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 lead-free ceramics with an excess of 5 mol% Na2CO3 exhibited the optimum properties with d33∼171 pC/N, kp∼30.0%. These results give a new way to low-temperature sintering Bi1/2Na1/2TiO3-based lead-free piezoelectric ceramic.
Physica B Condensed Matter 405(4):1228-1232. · 1.06 Impact Factor
