【作者】 梁兴华；

【导师】 王矜奉；

【作者基本信息】 山东大学 ， 材料物理与化学， 2007， 硕士

【摘要】 1952年，东京工业大学高木研究室对锆酸铅（PbZrO₃）、钛酸铅（PbTiO₃）固溶体(PbZr_xTi_1-xO₃)进行了深入研究，为压电陶瓷的广泛应用奠定了基础。半个多世纪以来，锆钛酸铅固溶体在研究和应用方面一直占据压电陶瓷的主导地位。但在PZT陶瓷中的PbO含量高达60％以上，铅基陶瓷在生产、使用和废弃处理过程中都给人类健康和生态环境造成较大损害。因此，探索无铅化压电陶瓷，研究环境协调性好的压电材料及其制品是电子元件行业的紧迫任务。钙钛矿结构铌酸盐基陶瓷是目前最具有替代PZT潜力的无铅压电陶瓷。但与PZT压电陶瓷相比，铌酸盐压电陶瓷有自身的缺陷，最主要的缺点是它的压电常数、机电耦合系较低。根据钙钛矿结构PZT在准同型相界附近，具有最高的压电活性的实验规律，本文拟系统探索铌酸盐基无铅压电陶瓷的组分与准同型相界的关系，重点探索准同型相界组分的压电介电性能，以期获得高压电性能的铌酸盐基无铅压电陶瓷的新体系。根据文献调研和本人的实验基础，本文选取了Na、K、Li摩尔比为0.53∶0.435∶0.035的x(Na_0.53K_0.435Li_0.035)NbO₃-y(Na_0.53K_0.435Li_0.035)SbO₃-z(Na_0.53K_0.435Li_0.035)TaO₃三元系作为研究对象。首先采用固相反应法分别合成了(Na_0.53K_0.435Li_0.035)NbO₃（简写为NKLN）、(Na_0.53K_0.435Li_0.035)SbP₃、(Na_0.53K_0.435Li_0.035)TaO₃粉料，分别制备了（1-x）(Na_0.53K_0.435Li_0.035)NbO₃-x(Na_0.53K_0.435Li_0.035)SbO₃（简写为NKLN—xSb），（1-x）(Na_0.53K_0.435Li_0.035)NbO₃-x(Na_0.53K_0.435Li_0.035)TaO₃（简写为NKLN-xTa）二元系以及（1-x-y）(Na_0.53K_0.435Li_0.035)NbO₃-x(Na_0.53K_0.435Li_0.035)SbO₃-y(Na_0.53K_0.435Li_0.035)TaO₃（简写为NKLN-xSb-yTa）三元系压电陶瓷，对其显微结构、压电及介电性能进行了系统的研究。实验测量揭示，随着Sb含量的增加，NKLN-xSb的压电常数d₃₃呈现先增大后减小的趋势，Sb的掺杂能够降低样品的四方—立方相变温度。实验发现，0.912(Na_0.53K_0.435Li_0.035)NbO₃-0.088(Na_0.53K_0.435Li_0.035)SbO₃具有较高的压电活性，压电应变常数d₃₃=246pC／N，机电耦合系数k_p=52％，k_t=48％，同时其居里温度T_C=259℃，四方-正交相变温度T_O-T=81℃。应用传统的固相反应法制备了NKLN-xTa系列无铅压电陶瓷，得到了致密性较高的陶瓷样品。实验发现，体系中Ta含量的增多，陶瓷的压电应变常数d₃₃先增大后减小，相对介电常数ε₃₃^T／ε₀逐渐增大，居里温度T_C和四方-正交相变温度T_O-T向低温方向移动。该系陶瓷具有很高的压电应变常数(在x=0.23时，d₃₃=271pC／N)，高的机电耦合系数k_p=51％，k_t=44％，较高的居里温度T_C=311℃，这些性能特征表明了该系陶瓷具有较好的应用前景。采用了传统的陶瓷工艺准备了NKLN-xSb-yTa系列陶瓷，其中（y=0.03，0.06，0.09，0.12，0.20）。探索出该系陶瓷的准同型相界，在准同型相界附近陶瓷具有优异性能，d₃₃达300～327pC／N，机电耦合系数k_p50％左右，相对质量密度高达95％及较高的居里温度T_C。d₃₃值高达327 pC／N的压电应变常数，超过目前文献报道的传统工艺铌酸盐系无铅压电陶瓷最高压电性能(d₃₃=300 pC／N，Salto Y., Takao H., Tani T., et al. Lead-free Piezoceramies. Nature, 2004, 432:84-87)。更多还原

【Abstract】 In 1952, Takagi Laboratory at Tokyo Institute of Technology for the first time conducted a thorough investigation into the solid solution PbZr_xTi_1-xO₃ composed of zirconate, PbZrO₃, and titanate PbTiO₃, which laid a foundation for the wide uses of these piezoceramics. Since then, the lead zirconium-titanate solid solution, PZT, has been in the leading position in piezoceramics for half a century. Because the content of PbO in PZT is higher than 60wt%, the Pb evaporation during sintering PZT and the discarded PZT products pollute the environment and do harm to human health. Therefore, it is an urgent task to probe and develop environment-friendly new industrial piezoceramic products.The perovskite-type niobate-based piezoceramics have been considered the best lead-free ceramics substituting for the PZT. In comparison with PZT, the niobate-based piezoceramics also have its shortcomings, the lower piezoelectric constants and electromechanical coupling factors are its major shortcomings. Based on PZT experimental regularity that perovskite-type PZT has good piezoelectric performance at the morphotropic phase boundary （MPB）, it was my plans to search the relation of the niobate piezoceramic compositions with the MPB and focus the studies on the piezoelectric, dielectric properties of the niobate piezoceramics at the MPB, so that the new lead-free piezoceramic system with high-piezoelectric properties can be obtained.Based on my experiments and others references, x (Na_0.53K_0.435Li_0.035)NbO₃-y(Na_0.53K_0.435Li_0.035)SbO₃-z(Na_0.53K_0.435Li_0.035)TaO₃ ternary system with a ratio of Na, K, Li: 0.53: 0.435:0.035, was chosen as studied object. The powers of (Na_0.53K_0.435Li_0.035)NbO₃ （abbreviated as NKLN） ,(Na_0.53K_0.435Li_0.035)SbO₃ and (Na_0.53K_0.435Li_0.035)TaO₃ were first prepared by the conventional solid-state reaction method respectively. Then （1-x）(Na_0.53K_0.435Li_0.035)NbO₃-x(Na_0.53K_0.435Li_0.035)SbO₃ （abbreviated as NKLN-xSb）,（1-x）(Na_0.53K_0.435Li_0.035)NbO₃-x(Na_0.53K_0.435Li_0.035)TaO₃（abbreviated as NKLN-xTa） and （1-x-y）(Na_0.53K_0.435Li_0.035)NbO₃-x(Na_0.53K_0.435Li_0.035)SbO₃-y(Na_0.53K_0.435Li_0.035)TaO₃ （abbreviated as NKLN-xSb-yTa） were also prepared respectively, their microstructures, electromechanical, piezoelectric and dielectric properties had been systematically investigated. It was found that with increasing Sb content, the piezoelectric constant d₃₃ ofNKLN-xSb increased and then decreased. With Sb increased, the orthorhombic to tetragonal polymorphic phase transition temperature shift towards lower temperatures. It was also found 0.912(Na_0.53K_0.435Li_0.035)NbO₃-0.088(Na_0.53K_0.435Li_0.035)SbO₃ has high-piezoelectric performance, its piezoelectric stress constant d₃₃ =246pC/N ,electromechanical coupling factor k_p=52%, k_t=48% , with its Curie temperature T_c=259℃:and T_O-T =81℃.Relative compact NKLN-xTa lead-free ceramics were prepared by conventional oxide solid-solution technique .The piezoelectric, electromechanical, dielectric properties of the ceramics were evaluated. It was found with the increase of Ta, the dielectric constant increased, the Curie temperature moved to lower temperature. NKLN-0.23Ta had a relatively high piezoelectric constant d₃₃ =271pC/N, highelectromechanical coupling factor k_p=51%, k_t =44%, and a high Curie temperatureof 311℃ These features indicate the ceramics is a promising candidate for substituting PZT in piezoelectric application fields.The NKLN-xSb-yTa （y=0.03, 0.06, 0.09, 0.12, 0.20） ceramic systems were prepared by conventional oxide solid-solution technique. The MPB of NKLN-xSb-yTa had been found and it was shown that the ceramics at MPB have excellent properties, piezoelectric constant d₃₃ ranging in 300-327pC/N. The piezoelectric constant d₃₃ of 327pC/N is higher than the highest one of niobate-based ceramics prepared by conventional processing reported by Japanese (d₃₃=300 pC/N, Salto Y., Takao H., Tani T., et al. Lead-free Piezoceramics. Nature, 2004,432: 84-87).更多还原