高居里温度铋层状结构铌酸铋钙(CaBi_(2)Nb_(2)O_(9))压电陶瓷

High Curie temperature bismuth layer-structured ferroelectric calcium bismuth niobate(CaBiNbO)piezoelectric ceramics

压电材料是一类重要的功能材料,在国民经济的多个领域有着重要应用.在能源、航空航天、国防工业等高端技术领域,压电材料的应用已经从常规使用转向极端环境下的服役,这要求压电材料和压电传感器能够在更高的温度下工作.作为高温压电材料,Aurivillius型铋层状结构铁电体由于其特殊的层状结构和较高的居里温度(Tc)引起了研究人员的广泛关注.铌酸铋钙(CaBi_(2)Nb_(2)O_(9))是一种典型的铋层状结构铁电体.由于具有较高的居里温度(Tc~940℃),近年来铌酸铋钙作为高温压电传感器材料受到了广泛的关注.本文主要介绍高居里温度铌酸铋钙压电陶瓷的研究进展.通过组分优化,铌酸铋钙的压电性能可得到显著提高.研究发现,A位离子取代比B位离子取代更有助于提高铌酸铋钙的压电性能,同时A位离子和B位离子共取代能够显著提高铌酸铋钙的压电性能.模板晶粒生长、放电等离子体烧结等织构化技术可进一步提高铌酸铋钙的压电性能.最新研究显示,性能优化的铌酸铋钙压电陶瓷的压电系数d33可达20 pC/N,同时居里温度Tc高达900℃,铌酸铋钙陶瓷是适合于压电传感器应用的一类高温压电材料.本文最后对提高铌酸铋钙压电性能提出了展望.

Piezoelectric materials play a key role in various kinds of modern electronic devices.High Curie temperature piezoelectric materials are required for piezoelectric sensors under critical conditions for nuclear power plants,automotive,aeronautic,and aerospace applications.These piezoelectric sensors usually withstand high temperature of 500℃or higher.To meet the requirements of these applications,piezoelectric materials must possess high piezoelectric performance and high electrical resistivity as well as high Curie temperature.The Aurivillius-type bismuth layer-structured ferroelectrics(BLSFs)are the most promising high-temperature piezoelectric materials because of their very high Curie temperature(Tc).Structurally,the BLSF compounds are composed of fluorite-like(Bi2O2)2+layers and perovskite-like(Am-1BmO3m+1)2-blocks,which arrange along the c axis alternately and regularly.The general formula is(Bi2O2)2+(Am-1BmO3m+1)2-,where A is a mono-,di-,or trivalent metallic ion(or their combination)suited to dodecahedral coordination;B is a transition metallic ion suited to octahedral coordination,and m is the number of BO6 octahedral in the perovskite-like blocks and varies from 1 to 4.In this paper,the crystal structure,piezoelectric properties(herein piezoelectric constant d33 value),and Curie temperature(Tc)of prototype BLSF ceramics have been summarized,and the summarized results indicate that the piezoelectric properties of high Tc BLSF compounds are very low.The prototype BLSF ceramics with Tc of>700℃exhibit low piezoelectric d33 value of no more than 10 pC/N,and the prototype BLSF ceramics with Tc of>900℃exhibit low piezoelectric d33 value of no more than 5 pC/N.Calcium bismuth niobate,CaBi_(2)Nb_(2)O_(9)(CBN),was firstly found and synthesized by Sweden scientist Aurivillius B,in 1949.But until 2005,the investigations on the piezoelectric properties of CBN were firstly reported by Yan H X and Reece M J.After that,the piezoelectric properties of CBN have attracted much attention.The compound CBN has a very high Curie temperature Tc of~940℃,and it is considered to be potential material as piezoelectric sensors and other electronic components for high-temperature applications.However,its particular bismuth layer-structured crystal structure restricts the rotation of the spontaneous polarization(Ps)in the two-dimensional orientation(a-b plane),and large coercive field(Ec)makes the material difficult to be poled sufficiently.The prototype CBN ceramic exhibits very low piezoelectric performance,with low piezoelectric d33 value of 5 pC/N.In this paper,the piezoelectric properties of bismuth layer-structure ferroelectric calcium bismuth niobate(CaBi_(2)Nb_(2)O_(9))piezoelectric ceramics have been summarized.The results indicate that A-site ions substitution is more effective than B-site ions substitution to enhance the piezoelectric properties of CaBi_(2)Nb_(2)O_(9) ceramics,and A-site and B-site ions co-substitution is more desirable to optimize the piezoelectric performance.The piezoelectric d33 can be promoted to>16 pC/N by compositions adjusting,while the Curie temperature remains higher than 900℃.Texture technologies,such as templated grain growth(TGG)and spark plasma sintering,have been introduced,and they are good methods to further enhance the piezoelectric performance of CaBi_(2)Nb_(2)O_(9) ceramics.The piezoelectric d33 can be promoted to higher than 20 pC/N by texture technologies.Overall,the CaBi_(2)Nb_(2)O_(9) ceramics are promising materials for high-temperature piezoelectric sensor applications.Finally,perspectives on how to further enhance the piezoelectric performance of CaBi_(2)Nb_(2)O_(9) ceramics are presented.