摘要在众多无铅压电陶瓷的体系中，碱金属铌酸盐基陶瓷具有良好的压电性能，被认为是最有可能取代铅基压电陶瓷的体系之一。然而纯的碱金属铌酸盐陶瓷（KNN）在压电常数d33等压电性能上相对于铅基压电陶瓷仍存在着较大差距，故需要依靠掺杂改性等方法，通过提高KNN陶瓷的烧结性能以获取更好的压电性能。BiFeO3（BFO）是至今发现的唯一能在室温下可表现出铁电/铁磁性共存的多铁材料，由于ANbO3和BiFeO3二者结构都为钙钛矿，可以实现无限比例固溶，故本文将采取在KNN体系中引入BFO作为第二组元，通过组分设计进行剪裁组分，研究BFO-KNN固溶体陶瓷的制备以及压电性能。81136

   本文采用传统固相烧结法制备了xBFO-(1−x)KNN(摩尔分数x=0，1%，2%)的固溶体陶瓷样品，对BFO-KNN体系中的成分、结构与烧成制度对材料压电、介电与铁电性能间的关系进行了系统的研究，通过XRD和SEM对陶瓷的结构和形貌进行表征，并测量了样品的介电频谱与电滞回线。

   具体研究内容如下：研究了BFO掺杂浓度与烧结温度对材料压电常数d33的影响，发现随着掺杂浓度的增加d33显著下降，1%的掺杂使d33从117pC/N减少到49pC/N，为不损失d33数值，BFO的掺杂含量应低于1%；固溶体陶瓷的烧结温度与d33的大小呈正相关关系，但温度变化产生的影响幅度相对较小。研究了BFO掺杂浓度与烧结温度对材料介电常数εr的影响，发现随着掺杂浓度的增加εr先增加后减小，其中970度下烧结的1%掺杂的样品的εr最大，在10KHz下εr=221；且烧结温度的增加会降低εr。研究了BFO掺杂浓度与烧结温度对剩余极化强度Pr和矫顽场Ec的影响，发现BFO的掺杂可有效提高样品的Ec和Pr，另外较低的烧结温度也会使Pr出现不同程度的增加，其中在980度℃下烧结的1%掺杂的样品得到了最大的Pr=19。4 uC/cm2,Ec=20。2 kv/cm。

毕业论文关键词：无铅压电陶瓷；KNN基；BFO掺杂；电学性能

毕业设计说明书外文摘要

Title   Research on the Preparation of BiFeO3-(K0。5Na0。5)NbO3 Solid Solution                                   

Abstract Lead-free piezoelectric ceramics (1–x)KNN−xBFO(x=0,1%,2% in mole) were prepared by the traditional solid state reaction。the relationship among the composition，structure，sintering process,piezoelectric, dielectric and ferroelectric properties was studied systematically。Several important conclusions can be summarized as follows：

   The relationship between the BFO content,sintering temperature and piezoelectric constant was investigated。It was found that the d33 significantly decreased with increasing the content of BFO。In order to remain a high vaule of d33,the doping content of BFO should be less than 1%。The sintering temperature was positively correlated with the vaule of d33,but the effect of sintering temperature on the vaule of d33 was quite less compared to the doping content of BFO。The relationship between the BFO content,sintering temperature and dielectric constant which was measured by the dielectric frequency spectrum was also studied。It was found that with the increasing the content of BFO,the εr of the ceramics firstly increased and then decreased,and the largest vaule of εr can be measured in the concentration of 1%,while the vaule of εr decreased with increasing the sintering temperature。Finally,the effects of the BFO content,sintering temperature on the ferroelectric parameter were investigated by measuring the hysteresis loop of the ceramics。The addition of BFO had an evident effect on increasing the Ec and Pr of the KNN ceramics,and low sintering temperature can lead to increase of Pr。