TY - JOUR
T1 - Phase transitional behavior, microstructure, and electrical properties in Ta-modified [(K0.458Na0.542) 0.96Li 0.04] NbO3 lead-free piezoelectric ceramics
AU - Chang, Yunfei
AU - Yang, Zu Pei
AU - Ma, Difei
AU - Liu, Zonghuai
AU - Wang, Zenglin
N1 - Funding Information:
This work was supported by the National Science Foundation of China (NSFC) (Grant No. 20771070), Natural Science Research Program of Shaanxi Province (Grant No. 2005 B16), and Doctorate Foundation of Shaanxi Normal University. FIG. 1. The XRD patterns of the ceramics with different Ta contents. FIG. 2. Raman spectra of the ceramics with different Ta contents. FIG. 3. The SEM photographs of the surface of the ceramics with different Ta contents [(a) x = 0.00 , (b) x = 0.05 , (c) x = 0.10 , (d) x = 0.15 , (e) x = 0.20 , and (f) x = 0.40 ]. FIG. 4. The SEM photographs of the fracture surface of the ceramics with different Ta contents [(a) x = 0.00 , (b) x = 0.10 , (c) x = 0.15 , (d) x = 0.20 , and (e) x = 0.40 ]. FIG. 5. The sintering temperature and the dielectric and piezoelectric properties of the ceramics with different Ta contents. FIG. 6. Temperature dependence of ε r for the ceramics with different Ta contents. (Inset) Variation of ε r for the ceramics measured from − 60 to 60 ° C . FIG. 7. Phase diagram of the ceramics with 0.00 ≤ x ≤ 0.40 . FIG. 8. log ( 1 / ε - 1 / ε m ) as a function of log ( T - T m ) for the ceramics with different Ta contents. (Inset) r as a function of x . FIG. 9. Temperature dependence of tan δ for the ceramics measured at 10 kHz with different Ta contents. FIG. 10. (a) P - E hysteresis loops of the ceramics with different Ta contents. (b) Variations of the remanent polarization ( P r ) and coercive field ( E c ) as a function of x .
PY - 2008
Y1 - 2008
N2 - Lead-free [(K0.458Na0.542)0.96Li 0.04] (Nb1-xTax)O3 ceramics were prepared by ordinary sintering technique. The effects of Ta content on the phase transitional behavior, Raman spectrum, microstructure, and dielectric, piezoelectric, and ferroelectric properties of the ceramics were investigated. X-ray diffraction results indicate that the phase structure undergoes a transition from orthorhombic to tetragonal phase with the increase in x. The small and large peaks observed in the Raman spectra can all be attributed to the internal modes of the NbO6 octahedron, and both ν5 and ν1 modes slightly shift to lower frequency numbers by increasing x. Ta substitution for Nb leads to the disappearance of the abnormal grain growth behavior, inhibits the grain growth, and improves the density of the ceramics. Increasing x leads to the different variations of dielectric constants before and after poling and makes the ceramics more relaxorlike. The proper substitution of Ta shifts the polymorphic phase transition (at To-T) to near room temperature, and a coexistence of orthorhombic and tetragonal phases is formed, which leads to significant enhancements of the electrical properties. For the ceramics with x=0.15, the electrical properties become optimum, which are as follows: piezoelectric coefficient d33 =298 pC/N, electromechanical coupling coefficient kp =0.52, dielectric constant εr =1195, dielectric loss tan δ=0.016, T o-T =35°C, Curie temperature TC =366°C, remanent polarization Pr =28.68 μC/ cm2, and coercive field Ec =7.14 kV/cm. These properties are much higher than those of previously reported (K,Na,Li) (Nb,Ta)O3 systems with K:Na=1:1.
AB - Lead-free [(K0.458Na0.542)0.96Li 0.04] (Nb1-xTax)O3 ceramics were prepared by ordinary sintering technique. The effects of Ta content on the phase transitional behavior, Raman spectrum, microstructure, and dielectric, piezoelectric, and ferroelectric properties of the ceramics were investigated. X-ray diffraction results indicate that the phase structure undergoes a transition from orthorhombic to tetragonal phase with the increase in x. The small and large peaks observed in the Raman spectra can all be attributed to the internal modes of the NbO6 octahedron, and both ν5 and ν1 modes slightly shift to lower frequency numbers by increasing x. Ta substitution for Nb leads to the disappearance of the abnormal grain growth behavior, inhibits the grain growth, and improves the density of the ceramics. Increasing x leads to the different variations of dielectric constants before and after poling and makes the ceramics more relaxorlike. The proper substitution of Ta shifts the polymorphic phase transition (at To-T) to near room temperature, and a coexistence of orthorhombic and tetragonal phases is formed, which leads to significant enhancements of the electrical properties. For the ceramics with x=0.15, the electrical properties become optimum, which are as follows: piezoelectric coefficient d33 =298 pC/N, electromechanical coupling coefficient kp =0.52, dielectric constant εr =1195, dielectric loss tan δ=0.016, T o-T =35°C, Curie temperature TC =366°C, remanent polarization Pr =28.68 μC/ cm2, and coercive field Ec =7.14 kV/cm. These properties are much higher than those of previously reported (K,Na,Li) (Nb,Ta)O3 systems with K:Na=1:1.
UR - http://www.scopus.com/inward/record.url?scp=48849083980&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=48849083980&partnerID=8YFLogxK
U2 - 10.1063/1.2957591
DO - 10.1063/1.2957591
M3 - Article
AN - SCOPUS:48849083980
SN - 0021-8979
VL - 104
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 2
M1 - 024109
ER -