Ag^+掺杂Na_(0.5)K_(0.5)NbO_3无铅压电陶瓷的无压烧结及性能研究

Properties of Ag^+ Doped Na_(0.5)K_(0.5)NbO_3 Lead-Free Piezoelectric Ceramics Fabricated by Normal Sintering

铅基压电陶瓷在制备、使用及废弃处理过程中都会造成环境污染,随着环保意识的增强,无铅压电陶瓷必将逐步替代铅基压电陶瓷。Na0.5K0.5NbO3是一种很有潜力的无铅压电陶瓷,掺杂各种元素提升Na0.5K0.5NbO3陶瓷的压电性能成为当今研究热点之一。本研究以Ag2O、Na2CO3、K2CO3、Nb2O5为原料,经750℃焙烧分别合成了Na0.5K0.5NbO3和AgNbO3粉料,再经配料、混料与成型,在1060℃埋粉烧结,制备出Ag+掺杂的Na0.5K0.5NbO3无铅压电陶瓷(xAgNbO3-(1-x)Na0.5K0.5NbO3,ANKN),并在较宽成分范围内(Ag+含量,x=0～50at%)系统研究了Ag+掺杂对ANKN陶瓷性能的影响。XRD结果表明,ANKN陶瓷的主相为钙钛矿型结构,当x>16at%,开始出现K5.75Nb10.85O30杂相,随着Ag掺杂量的增加,杂相的衍射峰增强。电学性能测试结果表明,当x<20at%,随Ag掺杂量的增加ANKN陶瓷的压电常数、介电常数等略有升高;当x>20at%,ANKN陶瓷的各项性能均开始降低;Ag掺加量为x=16at%时ANKN陶瓷性能最佳,压电常数d33达到110pC/N,平面机电耦合系数kp为30%,相对介电常数εr为358,居里温度Tc为300℃。

Although lead-based piezoelectric ceramics are widely used due to their excellent piezoelectric properties, discharged toxic PbO during processing causes environmental pollution, so there is an ever-increasing demand for lead-free piezoelectric materials. （Na, K）NbO3 base ceramics is a promising candidate for lead-free piezoelectric ceramics, and the doping effect on the （Na, K） NbO3 ceramics becomes a hot research. In this study, a series of Ag^＋ doped Na0.5K0.5NbO3 （ANKN） ceramics were synthesized by mixing and sintering Na0.5K0.5NbO3 and AgNbO3 powders at 1060 ℃ for 2 h, in which those two powders were first fabricated by calcining the raw materials of Ag2O, Na2CO3, K2CO3 and Nb2O5 at 750 ℃. The effect of Ag^＋ doping on electrical properties of ANKN ceramics within a wide composition range （Ag^＋ content, x=0-50 at%） was investigated. XRD patterns indicated that the main phase of ANKN is still perovskite-type structure similar to that of NKN. A K5.75Nb10.85O30-like phase appeared at x〉16 at%, and the intensity of the diffraction peaks increased with increasing Ag content. The piezoelectric constant and dielectric constant increased with increasing Ag content from 0 to 20 at%. The ANKN ceramics doped with 16 at% Ag showed the best performance in which the piezoelectric constant d33 and Curie temperature Tc reached 110 pC/N and 300 ℃, Planar electromechanical coupling factor kp and relative dielectric constant εr were 30 % and 358, respectively.