【作者】 王进松；

【导师】 李月明；

【作者基本信息】 景德镇陶瓷学院 ， 材料学， 2009， 硕士

【摘要】 本文以K_xNa_1-xNbO₃（简写为NKN）陶瓷为主要研究对象,开展以下两部分研究工作。一是粉体制备:首先采用熔盐法合成NKN粉体,研究熔盐法制备NKN粉体的工艺参数:如熔盐含量、合成温度、熔盐种类对NKN粉体的影响。研究表明应用熔盐法很难一次性制备出各向异性的NKN粉体,因此,采用二次熔盐法来制备片状NaNbO₃模板粉体。二是压电陶瓷制备:首先以熔盐法制备NKN粉体为原料,采用固相法制备NKN压电陶瓷并对其性能进行研究;在制备纯的NKN压电陶瓷的基础上添加助烧剂ZnO和CuO,对NKN压电陶瓷进行改性研究。其次以片状NaNbO₃粉体为模板,借助流延成型工艺,采用反应模板法制备(Na_0.5K_0.5)_0.94Li_0.06NbO₃（简称NKLN）织构型陶瓷。研究了熔盐含量、合成温度以及熔盐种类对NKN粉体形貌的影响。结果表明:通过熔盐法可以在650℃—850℃下合成纯钙钛矿结构的NKN粉体;随着合成温度的升高,粉体形貌从圆球状转变为立方结构,进一步提高合成温度,粉体形貌开始变得不规则;此外,合成粉体的尺寸随着熔盐含量的增加而增大,且粉体团聚现象明显减弱。以Na₂CO₃-K₂CO₃（摩尔比1:1）为熔盐,在熔盐与反应物的总质量比为1:3,合成温度为800℃保温4 h时制备出形貌规制、晶粒均匀的NKN粉体。研究了熔盐含量和合成温度对Bi_2.5Na_3.5Nb₃O₁₈（简称BNN5）粉体形貌的影响,研究发现随着合成温度的升高BNN5粉体的尺寸逐渐增大,温度继续升高,粉体尺寸增加并不明显;随着熔盐含量的增加,BNN5粉体晶粒尺寸逐渐增大。在1100℃下保温3h,在熔盐与反应物的总质量比为1:1时,可以制备出尺寸较大（平均粒径15μm）、边缘相对整齐的前躯体BNN5粉体。以上述条件制备的BNN5为前躯体,采用熔盐法在950℃下,熔盐与反应物的总质量比为1:1时,可以制备出大尺寸和高度各向异性的NaNbO₃模板晶粒粉体。以熔盐法合成的NKN粉体为原料,添加适量的ZnO和CuO为烧结助剂,采用普通陶瓷制备技术制备NKN陶瓷,研究了烧结助剂和制备工艺条件对NKN压电陶瓷性能的影响。结果表明:当烧成温度为1080℃时体积密度达到最大值3.81g/cm³,在1060℃保温2h所制备NKN压电陶瓷具有优异的压电性能和介电性能,其中压电常数d₃₃=124 pC/N,机电耦合系数k_p=0.27,介电常数ε₃₃^T/ε₀=345,居里温度T_c达406℃,P_r=20.62μC/cm²,E_c=3.45 kV/mm。以片状NaNbO₃为反应模板剂,按照(Na_0.5K_0.5)_0.94Li_0.06NbO₃化学计量,以固相法合成的NaNbO₃,KNbO₃和LiNbO₃为反应物,采用RTGG法制备NKLN织构化压电陶瓷,研究制备工艺对NKLN织构化压电陶瓷性能的影响。研究发现:经1080℃烧结所制备NKLN的陶瓷体积密度达到最大值3.80g/cm³,并具有优异的压电性能和介电性能,其中压电常数d₃₃=118 pC/N,机电耦合系数k_p=0.354,介电常数ε₃₃^T/ε₀=357,居里温度T_c达429℃。结果表明采用RTGG技术制备的NKLN压电陶瓷沿（001）方向取向性生长明显,所得织构陶瓷各向异性生长比较显著。更多还原

【Abstract】 In this dissertation,K_xNa_1-xNbO₃（abbreviated as NKN） ceramics were selected as the investigation object,and the main research contents were as follows.The first study content was the synthesis of NKN powder by the molten salt synthesis method（abbreviated as MSS）,and the effects of synthesizing temperature,the molten salt species and amount of salt were studied.It was found that the NKN powder with high degree anisotropy could not been immediately prepared by MSS.Therefore,a novel processing method was used to synthesize plate-like NaNbO₃ particles.The second study content was preparation of piezoelectric ceramics.（1） The NKN powder synthesized by the MSS method was used to prepare NKN piezoelectric ceramics by conventional solid state method.Then 1.0 mol%ZnO and 1.0 mol%CuO was added as sintering agent,Meanwhile the effect of structure,piezoelectric, ferroelectric and dielectric properties were investigated.（2） The textured (Na_0.5K_0.5)_0.94Li_0.06NbO₃（abbreviated as NKLN） piezoelectric ceramics were fabricated by the templated grain growth（RTGG） techniques with the plate-like NaNbO₃ particles prepared by two step molten salt synthesis method as template particles.The dependence of the molten salt content,the synthesized temperature as well as the molten salt species on the grain growth and the morphology of the NKN powder were studied.The results present that the NKN powders with pure perovskite structure were synthesized by the molten salt method in the molten salt fluxes of Na₂CO₃-K₂CO₃（mol 1:1） at 700℃～850℃for 4 h.The results reveal that the crystal morphology of NKN powder changes from spheroid to cube,and then become irregular with temperature increasing.In addition,the grain size increased and the agglomeration of the NKN powders decreases clearly with the molten salt content increasing.The optimal morphology of NKN powder can be obtained with a 1:3 salt-to-oxide ratio in Na₂CO₃-K₂CO₃ flux at 800℃for 4 h.The dependence of the molten salt content and the synthesized temperature on the morphology of the Bi_2.5Na_3.5Nb₃O₁₈（BNN5）powder was studied.It can be found that the grain size increased and then without changing with the increase of molten salt content and synthesizing temperature.The optimal technique for preparing large-size and high degree anisotropic BNN5 template particles are as follow:NaCl used as salt fluxes, salt-to-oxide ratio is 1:1,the synthesizing temperature is at 1100℃and soaking time is about 4 h.Using this precursor（BNN5）,plate-like NaNbO₃ particles could be prepared with 1:1 salt-to-oxide ratio in NaCl flux at 950℃for 3 h.The NKN ceramics were prepared by conventional solid phase sintering, using the NKN powders synthesized by the molten salt method as raw materials and adding right amount ZnO and CuO as sintering agent.The effect of the sintering agent and the preparation process on the properties of NKN ceramics was studied.The results show that the maximum of the bulk density of NKN ceramic sintered at 1080℃for 2h is 3.81 g/cm³.The excellent dielectric and piezoelectric properties of NKN ceramic sintered at 1060℃were obtained and the properties were as follow:d₃₃=124 pC/N,ε₃₃^T/ε₀=345, T_c=406℃,k_p=0.27,P_r=20.62μC/cm² and E_c=3.45 kV/mm.The textured(Na_0.5K_0.5)_0.94Li_0.06NbO₃ ceramics were fabricated by the reaction templated grain growth（RTGG） technique using the plate-like NaNbO₃ powder as template particles,using NaNbO₃,KNbO₃ and LiNbO₃ as reactants.The preparation technology of textured NKLN ceramics prepared by the RTGG was studied.It can be found that the maximum of the bulk density of NKLN ceramic sintered at 1080℃for 2h is 3.81 g/cm³.The excellent dielectric and piezoelectric properties of the textured NKLN ceramics were obtained and the properties were as follow:d₃₃=118 pC/N,ε₃₃^T/ε₀=357,T_c= 429℃,k_p=0.354.The results reveal that the textured NKLN ceramics prepared by RTGG method were the（001） orientated ceramics obviously and appeared to be anisotropy.更多还原