冲击波加载下孔隙率对Pb_(0.99)(Zr_(0.95)Ti_(0.05))_(0.98)Nb_(0.02)O_3铁电陶瓷去极化性能的影响

制备了四种不同孔隙率的Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3铁电陶瓷,并研究了冲击波作用下孔隙率对陶瓷去极化性能的影响.研究表明:短路负载条件下陶瓷的放电波形不随孔隙的加入而改变,均为方波.多孔陶瓷的放电脉冲幅度较低,脉冲宽度较长.释放的电荷量随着孔隙率的增加而减小,与静态电滞回线测试结果一致.多孔陶瓷具有较低的冲击阻抗,改善了与封装介质的阻抗匹配.用Lysne模型拟合了材料在高电阻负载条件下的放电行为,并指出高电阻负载条件下材料的介电常数是静态介电常数的4—5倍,而且材料的介电常数随孔隙率的增加而减小.冲击波通过样品以后,电路的放电时间常数随着孔隙率的增大而增大.随着电阻的增大,样品负载电压增高,材料铁电-反铁电相变受到抑制,电流上升沿变缓,致密陶瓷出现了击穿现象.

Porosity effects on depoling characteristics of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics under shock wave load

Four kinds of Pb_0.99(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ ferroelectric ceramics with different porosities are prepared, and the porosity effects on the depoling characteristics of those samples under shock wave load are investigated. The results show that under short circuit condition, the releasing current waveforms are in the form of square pulse for all samples. The amplitude of the current pulse decreases, but the width increases with the porosity increasing. The releasing charge decreases with the porosity increasing, which is consistent with the measurement by P-E loop. Porous ceramics has lower shock impedance, which improves the impedance match to the encapsulation medium. The depoling characteristics of those samples under high resistance load are simulated well by Lysne model. The results reveal that the dielectric constant of the sample is 4—5 times larger than that under static state, moreover, it decreases with porosity increasing. After the shock wave passing through the sample, the discharging time constant increases with porosity increasing. As the load increases, the rising edge becomes less steep for the restrain of the ferroelectric phase-antiferroelectric phase transformation under high electric field, and the breakdown happens to the dense ceramics.