KNN基无铅压电陶瓷的掺杂改性和微观机理研究
发布时间：2018-09-11 17:59
【摘要】：铅基压电陶瓷在压电领域有较广泛的应用,然而铅元素的毒性限制了它的发展。随着人们环保意识的增强,无铅的碱性铌酸盐压电材料得到了重点的关注。通过掺杂改性以及流延工艺制备出的铌酸盐系(KNN)压电材料,具有可以与PZT(铅基压电陶瓷)相匹敌的性能。因此,制备高性能铌酸钾钠等无铅压电陶瓷是现在的热门研究课题。本文主要通过掺杂改性、两步烧结以及流延法逐步提高KNN陶瓷压电性能。陶瓷的两相共存可以大大提高KNN基陶瓷的压电性能,实验采用CaTiO_3、BaTiO_3以及BaZrO_3复合掺杂,制备(0.91-x)K_(0.5)Na_(0.5)NbO_3-0.03BaTiO_3-0.06BaZrO_3-xCaTiO_3(简写为:(0.91-x)KNN-BT-BZ-xCT)。通过改变CaTiO_3掺量,使得陶瓷菱方-正交两相共存区移向室温附近,获得陶瓷性能成倍提高。通过KNN相图看出,由于碱金属的存在,KNN陶瓷在烧结中容易使碱金属挥发,出现成分分凝,使得掺杂在液相区析出,导致陶瓷性能降低。实验中采用两步烧结法(TSS),有效的降低并阻止了分凝,减小晶粒,提高了陶瓷的成分均一化程度。为了进一步提高掺杂后陶瓷的性能,以片状NN(NaNbO_3)作为模板,用流延法制备(001)面定向生长的0.90KNN-BT-BZ-0.01CT基陶瓷。通过三元系掺杂改性,当x取值0.01时,由于出现了准同型相界(PPT),(0.91-x)KNN-BT-BZ-xCT陶瓷的压电和介电性能达到了最佳,为185PC/N。和SSS(普通固相法)烧结陶瓷相比,TSS烧结陶瓷的致密度要高出3%,压电常数提高18%,为219 PC/N。通过XRD和EDS物相分析,TSS法烧结陶瓷物相具有更低的碱金属烧损量。流延法中NN模板的制备至关重要,首先采用熔盐法制备前驱体BNN,后又运用熔盐法及产生的拓扑化学反应制备了各向异性的片状NaNbO_3模板晶粒。当模板含量为5%时,织构压电陶瓷材料性能达到最佳,制备陶瓷的织构度f达到86%。和非织构陶瓷相比,织构陶瓷使得陶瓷的轴率(c/a)减小,介电温谱曲线中居里温度区域以及介电常数峰变窄,提高了陶瓷介电常数的温度非线性。通过不同方法制备的压电陶瓷中,织构法制备的压电陶瓷具有最佳的压电常数和机电转化效率,d33和Kp分别达到236PC/N和42.2%。
[Abstract]:Lead-based piezoelectric ceramics are widely used in piezoelectric field, however, the toxicity of lead element limits its development. With the increasing awareness of environmental protection, lead-free basic niobate piezoelectric materials have received great attention. The niobate series (KNN) piezoelectric materials prepared by doping modification and casting process have the properties of being comparable to those of PZT (lead based piezoelectric ceramics). Therefore, the preparation of lead-free piezoelectric ceramics such as potassium sodium niobate is a hot research topic. In this paper, the piezoelectric properties of KNN ceramics were improved by doping modification, two step sintering and casting method. The piezoelectric properties of KNN based ceramics can be greatly improved by the coexistence of two phases. (0.91-x) K _ (0.5) Na_ _ (0.5) NbO_3-0.03BaTiO_3-0.06BaZrO_3-xCaTiO_3 (abbreviated as (0.91-x) KNN-BT-BZ-xCT) was prepared by CaTiO_3,BaTiO_3 and BaZrO_3 doping. By changing the content of CaTiO_3, the coexisting region of rhombohedral and orthonormal phases is moved to the room temperature, and the properties of the ceramics are improved exponentially. The KNN phase diagram shows that the alkali metal is easily volatilized in the sintering process, and the component segregation occurs, which makes the doping precipitate in the liquid region, which results in the decrease of the ceramic properties. In the experiment, the two-step sintering method (TSS), can effectively reduce and prevent the segregation, reduce the grain size, and improve the homogenization of the ceramic composition. In order to further improve the properties of the doped ceramics, the (001) plane oriented 0.90KNN-BT-BZ-0.01CT based ceramics were prepared by using flake NN (NaNbO_3) as template. The piezoelectric and dielectric properties of the quasi homogeneous phase boundary (PPT), (0.91-x) KNN-BT-BZ-xCT ceramics were optimized when x value was 0. 01 by doping the ternary system, which was 185 PC / N. Compared with SSS sintered ceramics, the density of Sintered Ceramics is 3 times higher, and the piezoelectric constant is increased by 18 PC/N. to 219 PC/N.. By XRD and EDS phase analysis, the phase of ceramic sintered by TSS has lower alkali metal burning loss. The preparation of NN template is very important in the casting method. Firstly, the precursor BNN, is prepared by molten salt method, and then the anisotropic grain of NaNbO_3 template is prepared by molten salt method and topological chemical reaction. When the template content is 5, the properties of the textured piezoelectric ceramics are the best, and the textural degree f of the prepared ceramics is up to 86. Compared with the nonwoven ceramics, the axial ratio (c / a) of the ceramics decreases, the Curie temperature region and the dielectric constant peak in the dielectric temperature curve line become narrower, and the temperature nonlinearity of the dielectric constant is improved. Among the piezoelectric ceramics prepared by different methods, the textured piezoelectric ceramics have the best piezoelectric constant and electromechanical conversion efficiency (D33 and Kp) up to 236PC/N and 42.2, respectively.
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM282
本文编号：2237435
[Abstract]:Lead-based piezoelectric ceramics are widely used in piezoelectric field, however, the toxicity of lead element limits its development. With the increasing awareness of environmental protection, lead-free basic niobate piezoelectric materials have received great attention. The niobate series (KNN) piezoelectric materials prepared by doping modification and casting process have the properties of being comparable to those of PZT (lead based piezoelectric ceramics). Therefore, the preparation of lead-free piezoelectric ceramics such as potassium sodium niobate is a hot research topic. In this paper, the piezoelectric properties of KNN ceramics were improved by doping modification, two step sintering and casting method. The piezoelectric properties of KNN based ceramics can be greatly improved by the coexistence of two phases. (0.91-x) K _ (0.5) Na_ _ (0.5) NbO_3-0.03BaTiO_3-0.06BaZrO_3-xCaTiO_3 (abbreviated as (0.91-x) KNN-BT-BZ-xCT) was prepared by CaTiO_3,BaTiO_3 and BaZrO_3 doping. By changing the content of CaTiO_3, the coexisting region of rhombohedral and orthonormal phases is moved to the room temperature, and the properties of the ceramics are improved exponentially. The KNN phase diagram shows that the alkali metal is easily volatilized in the sintering process, and the component segregation occurs, which makes the doping precipitate in the liquid region, which results in the decrease of the ceramic properties. In the experiment, the two-step sintering method (TSS), can effectively reduce and prevent the segregation, reduce the grain size, and improve the homogenization of the ceramic composition. In order to further improve the properties of the doped ceramics, the (001) plane oriented 0.90KNN-BT-BZ-0.01CT based ceramics were prepared by using flake NN (NaNbO_3) as template. The piezoelectric and dielectric properties of the quasi homogeneous phase boundary (PPT), (0.91-x) KNN-BT-BZ-xCT ceramics were optimized when x value was 0. 01 by doping the ternary system, which was 185 PC / N. Compared with SSS sintered ceramics, the density of Sintered Ceramics is 3 times higher, and the piezoelectric constant is increased by 18 PC/N. to 219 PC/N.. By XRD and EDS phase analysis, the phase of ceramic sintered by TSS has lower alkali metal burning loss. The preparation of NN template is very important in the casting method. Firstly, the precursor BNN, is prepared by molten salt method, and then the anisotropic grain of NaNbO_3 template is prepared by molten salt method and topological chemical reaction. When the template content is 5, the properties of the textured piezoelectric ceramics are the best, and the textural degree f of the prepared ceramics is up to 86. Compared with the nonwoven ceramics, the axial ratio (c / a) of the ceramics decreases, the Curie temperature region and the dielectric constant peak in the dielectric temperature curve line become narrower, and the temperature nonlinearity of the dielectric constant is improved. Among the piezoelectric ceramics prepared by different methods, the textured piezoelectric ceramics have the best piezoelectric constant and electromechanical conversion efficiency (D33 and Kp) up to 236PC/N and 42.2, respectively.
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM282
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