以片状NaNbO3晶粒为模板,以K4CuNb8O23(KCN)为助烧剂,通过丝网印刷技术制备出晶粒定向的K0.45Na0.55NbO3(KNN)无铅压电陶瓷.片状的NaNbO3模板是以铋层状Bi2.5Na3.5Nb5O18为前驱物,通过熔盐-拓扑微观反应制得.织构化(K0.45Na0.55)NbO3陶瓷的晶粒定向程度达到95％,其定向晶粒沿丝网印刷方向平行排列,块体的相对密度达到92％.在平行和垂直于丝网印刷方向的两个面上,织构化(K0.45Na0.55)NbO3陶瓷表现出不同的定向程度,且其介电、铁电和压电性能均明显优于无织构化陶瓷.介电常数εr、压电系数d33、机电耦合系数kp在平行于丝网印刷方向的表面上,分别提高了75％、44％、42％；在垂直于丝网印刷方向的表面上分别提高了35％、30％、35％.相对于目前其它的晶粒定向技术,丝网印刷方法既简单又高效.
Grain oriented K0.45Na0.55Nb03 (KNN)lead-free piezoceramics with sintering aid K4CuNb8O23 (KCN) were fabricated by screen-printing technique,using plate-like NaNbO3 as templates.The plate-like NaNbO3 template particles were synthesized from bismuth layer-structured Bi2.5Na3.5Nb5O18 precursors by the topochemical micro-crystal conversion method.The textured KNN ceramics showed brick-wall-like grains which aligned parallel to the screen-printing direction.The screen-printed KNN ceramics possessed both a high grain orientation (Lotgering factor f=95％) and a relative high density (92％ of theoretical density).The orientation degree and electrical properties of textured (K0.45Na0.55)NbO3 ceramics exhibited anisotropic feature in the parallel (sp//) and perpendicular (sp⊥) plane.Compared with the random oriented ceramics with same composition,the dielectric constant εr, piezoelectric constant d33,and electromechanical coupling coefficient kp were increased by about 75％,44％ and 42％ in sp// plane,respectively,and about 35％,30％ and 35％ in spp⊥ plane,respectively.Screen-printing is a simple and effective method for the fabrication of grain oriented lead-free piezoelectric ceramics.
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