Effects of Li Substitution and Sintering Temperature on Properties of Bi0.5（Na,K）0.5TiO3 Lead-Free Piezoelectric Ceramics

Bi0.5 （Na0.72K0.28- x Lix ）0.5 TiO3 （BNKLT- 100x） lead-free piezoelectric ceramics are synthesized by conventional solid state sintering techniques. The dielectric and piezoelectric properties of the BNKLT-100x ceramics as a function of Li content are systematically investigated. It is found that not only Li content but also the sintering temperature has a strong effect on the piezoelectric properties of BNKLT. The piezoelectric constant d33 Of BNKLT varies from 120 to 252pC/N in the Li content range from 0.03 to 0.16. In the sintering temperature range from 1080 to 1130℃, the d33 value of BNKLT-6 changes from 200pC/N to 252pC/N. The BNKLT-6 sample sintered at 1100℃ has the highest piezoelectric constant d33 of 252pC/N, with the electromechanical coupling factors kp of 0.32 and kt of 0.44.     

Bi2223/Ag超导带材的超低频交流损耗

鉴于银包套的铋系高温超导带材作为电工商品化材料的前景己十分看好，我们利用直流电输运的四引线（DCE）和交流磁化率（ACS）两种方法从实验和理论上研究了银包套的铋系高温超导带材Bi2223/Ag的超低频和低频交流损耗（Q）及数值模拟，测量频率范围从0.001到200Hz。在超低频和低频范围内，也就是低的磁场和电流扫描速度时，两种方法的结果相一致，Q随频率增加，但是在较高一点的频率下ACS方法测量到Q随频率增加而关小。然而，DCE方法却发现Q随电流扫描速度增加而单调地增加。数值模拟研究的结果证明，上述两种实验方法所得到的结果可以用巨磁通蠕动理论予以解释，我们的研究结果说明了电输运方法和磁测量方法各有一定的特征。