水热法制备铌酸钾钠基无铅压电陶瓷粉体的研究

发布时间：2018-03-19 11:51

本文选题：水热法　切入点：两步水热法　出处：《南京航空航天大学》2010年硕士论文　论文类型：学位论文

【摘要】： 本文分别采用异丙醇辅助水热法和两步水热法在240oC下成功合成了钙钛矿结构的(K,Na)NbO_3无铅压电陶瓷粉体。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)研究了原料中K/(K+Na)和(K+Na)/Nb摩尔比对产物粉体的物相结构和微观形貌的影响。结果表明异丙醇辅助水热法易于合成富钾或富钠的单相(K,Na)NbO_3固溶体。而合成K/Na接近1的(K,Na)NbO_3固溶体时,得到的粉体为富钾的(K,Na)NbO_3固溶体和富钠的(K,Na)NbO_3固溶体多相共存的混合物。然而两步水热法可以通过调节第二步水热反应中原料的比例很好的控制产物中K/Na的比例。对富钾的(K,Na)NbO_3固溶体和富钠的(K,Na)NbO_3固溶体多相共存的混合物在不同的温度进行后期热处理实验,XRD结果显示在900 oC下保温两个小时后物相由最初的多相共存转变为单相的(K,Na)NbO_3固溶体。为了提高(K,Na)NbO_3的压电性能,在水热合成(K,Na)NbO_3粉体的基础上,对其进行了Sb元素的掺杂,成功得到了单相的(K_(0.7)Na_(0.3))(Nb_(0.95)Sb_(0.05))O_3粉体。采用XRD、Raman散射和SEM等方法研究了Sb元素掺杂对水热合成(K,Na)(Nb, Sb)O_3粉体的物相结构和形貌的影响。结果表明随着Sb元素掺杂量的增加,得到粉体的物相从富钾相和富钠相共存逐渐转变为单相的(K, Na)(Nb, Sb)O_3固溶体,并且其形貌由无规团聚状变化为规则的六角状形貌。本文还进行了240oC时不同反应时间下水热合成(K, Na)(Nb, Sb)O_3粉体的实验,通过测试不同反应时间得到的产物的物相结构和粉体形貌,我们提出了一种可能的(K, Na)(Nb, Sb)O_3固溶体的水热合成机理,探讨了Sb元素掺杂对物相结构和形貌的影响机制。以水热法合成的单相的K (Nb_(0.95)Sb_(0.05))O_3和Na (Nb_(0.95)Sb_(0.05))O_3粉体为原料,采用传统烧结工艺制备了无铅压电陶瓷。与传统固相法相比,水热法制备的压电陶瓷其体内气孔率下降,密度增大,晶界强度增强,出现穿晶断裂。运用阻抗分析仪和铁电分析仪测试其介电、压电、铁电性能,得到压电常数d33为146pC/N,机电耦合系数kp为42%左右,品质因数Qm为63左右,相对介电常数εr为750,介电损耗tanδ为0.03,并且剩余极化强度Pr有较明显的提高,达到了30μC/cm2以上。
[Abstract]:Lead-free piezoelectric ceramic powders with perovskite structure have been successfully synthesized by isopropanol assisted hydrothermal method and two-step hydrothermal method at 240oC, respectively. K _ (+) K _ (+) Na) in raw materials has been studied by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The effects of molar ratio of K and K Na)/Nb on the phase structure and micromorphology of the product powders were investigated. The results showed that the potassium rich or sodium rich monophase KNbO3 solid solution was easy to be synthesized by isopropanol assisted hydrothermal method, and when the K / Na ratio was close to 1, the K / Na NbO _ 3 solid solution could be synthesized, and when the K / Na ratio was close to 1, the NbO _ 3 solid solution could be synthesized by isopropanol assisted hydrothermal method. The obtained powder is a mixture of potassium rich Knao NbO _ 3 solid solution and sodium rich K _ 2O _ 3 solid solution. However, the two-step hydrothermal method can control the ratio of K / Na in the product very well by adjusting the ratio of the raw material in the second step hydrothermal reaction. The XRD results show that the phase changes from the initial multiphase coexistence to the single-phase KNaNbO3 solid solution after holding at 900oC for two hours after post-heat treatment at different temperatures for the mixture of KNaNaNbO3 solid solution and sodium rich KNaNbO3 solid solution at different temperatures, and the XRD results show that the phase changes from the initial multiphase coexistence to the single-phase KNaNbO3 solid solution after holding at 900oC for two hours. In order to improve the piezoelectric properties of NbO3, the SB element was doped on the basis of hydrothermal synthesis of NbO3 powder. In this paper, we have successfully obtained the single-phase single phase KDD-0.7NaTi-0.3NbStack-0.95SbStack-0.05SnO3 powder. The effect of SB doping on the phase structure and morphology of Sb)O_3 powder was studied by means of XRD-Raman scattering and SEM. The results show that with the increase of SB doping amount, the effect of SB doping on the phase structure and morphology of Sb)O_3 powder is studied. The results show that the effect of SB doping on the phase structure and morphology of Sb)O_3 powder is studied with increasing the doping amount of SB element, and the effect of SB element doping on the phase structure and morphology of Sb)O_3 powder is studied. The phase of powder was gradually changed from the coexistence of potassium rich phase and sodium rich phase to a single phase solid solution of K, Na-Nb, Sb)O_3. Moreover, the morphologies of the products changed from random agglomeration to regular hexagonal morphologies. Experiments were also carried out on the hydrothermal synthesis of K, Na-Nb, Sb)O_3 powders at different reaction times at 240 OC. The phase structure and morphology of the products obtained at different reaction times were tested. We propose a possible hydrothermal synthesis mechanism of K, Na-Nb, Sb)O_3 solid solution, and discuss the influence mechanism of SB doping on the phase structure and morphology. The lead-free piezoelectric ceramics were prepared by traditional sintering process from the single phase K-NbDX 0.95 SbO _ 3 and Na _ NbM _ (0.95) SbDO _ 3 powders synthesized by hydrothermal method. Compared with the conventional solid state method, the bulk porosity and density of the piezoelectric ceramics prepared by hydrothermal method decreased and the density increased. The dielectric, piezoelectric and ferroelectric properties were measured by impedance analyzer and ferroelectric analyzer. The piezoelectric constant D33 was 146pC / N, the electromechanical coupling coefficient (KP) was about 42%, and the quality factor (QM) was about 63. The relative dielectric constant 蔚 r is 750, the dielectric loss tan 未 is 0.03, and the residual polarization intensity pr is obviously increased to more than 30 渭 C / cm 2.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2010
【分类号】：TQ174.75

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