Peng QI
,
Jinfeng WANG
,
Baoquan MING
,
Juan DU
,
Xinghua LIANG
,
Limei ZHENG
材料科学技术（英文）
Lead-free piezoelectric ceramics (Na0.5K0.5-xLix)NbO3 (x=0.057–0.066) were synthesized by an ordinary sintering technique. Substituting Li for K can lead to structural distortion, which improves the Curie temperature (TC) greatly. By adding appropriate LiNbO3 content, piezoelectric constant d33 values reach 202–212 pC/N. Electromechanical coefficients of the planar mode reach 44.4%–46.8%. The dielectric loss is below 2.6%, which is much lower than reported (about 50%). The TC of (Na0.5K0.5-xLix)NbO3 (x=0.057–0.066) is in the range of 490–510oC, at least 70oC higher than that of pure (Na0.5K0.5)NbO3 ceramics. The results show that (Na0.5K0.5-xLix)NbO3 ceramic is a kind of good lead-free high-temperature piezoelectric material.
关键词:
Lead-free
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Changpeng LI
,
Jinfeng WANG
,
Wenbin SU
,
Hongcun CHEN
,
Wenxin WANG
材料科学技术（英文）
The electrical properties of (Nb, Li)-doped SnO2 ceramics as a new varistor material were investigated. The sample 97.95%SnO2.0.50%Li2O.0.05%Nb2O5 (mol fraction) sintered at 1450ºC possess the highest density (r=6.77 g/cm3) and nonlinear electrical coefficient (a=11.6). The substitution of Sn4+with Li+ increases the concentration of oxygen vacancies, together with the formation of solid solution, which will increase the sintering rate greatly and decrease the optimized sintering temperature. The substitution of Sn4+with Li+ and the variation of temperature play very important effects on the densities, dielectric constant, nonlinear electrical properties and other characteristics of the samples. The properties of the grain boundary barrier and the microstructural characteristics were investigated to ensure the effect of the dopants and the temperature. A grain boundary defect barrier model was used to illustrate the grain boundary barriers formation in SnO2-Li2O-Nb2O5 varistors.
关键词:
Varistors
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