【作者】 张雷；

【导师】 沈建兴；

【作者基本信息】 山东轻工业学院 ， 材料学， 2008， 硕士

【摘要】 压电陶瓷广泛应用于压电传感觉器,超声换能器和其它电子器件。但是大部分电子器件使用的都是含铅压电陶瓷,其中铅含量高达60%以上。铅是一种有毒物质,由于铅的易挥发性,在生产、制备、使用及废弃处理中都会对环境造成极大的污染。因此发展无铅压电陶瓷来代替含铅压电陶瓷已经刻不容缓。(Na0.5K0.5)NbO3 (KNN)由于其优异的压电性能而成为候选材料。本论文采用传统的制备工艺,在常压烧结的条件下制备了0.94(Na0.5K0.5)NbO3–xLiSbO3–yLiNbO3无铅压电陶瓷,并对其物相结构、压电、介电性能进行了研究。采用传统陶瓷制备方法制备了0.94(Na0.5K0.5)NbO3–xLiSbO3–yLiNbO3 (NKNLS)体系无铅陶瓷,研究了不同LiSbO3和LiNbO3的量对NKNLS无铅压电陶瓷材料的密度、相结构、显微结构和电学性能的影响。X射线衍射(XRD)表明过量的LiNbO3或者LiSbO3都不能使样品形成完全纯的钙钛矿相,而且有钨青铜结构的第二相K3Li2Nb5O15生成。只有适量的LiNbO3和LiSbO3才能形成纯的钙钛矿相。通过扫描电镜(SEM)分析可知NKNLS无铅压电陶瓷体系的显微结构也由于LiNbO3和LiSbO3含量的不同而表现出很大差异。当x=0.03,y=0.03时,0.94(Na0.5K0.5)NbO3–xLiSbO3–yLiNbO3无铅压电陶瓷表现出优越的压电性能。同时研究了烧结温度对0.94(Na0.5K0.5)NbO3–0.03LiSbO3–0.03LiNbO3(NKNLS–3)的密度、相结构、显微结构和电学性能的影响。XRD分析表明当烧结温度≤1080℃时,NKNLS–3样品都是纯的钙钛矿相结构,当烧结温度>1080℃时,有钨青铜结构的第二相K3Li2Nb5O15出现,从而恶化了其压电性能。通过对样品密度的测量可知最佳烧结温度为1080℃。当烧结温度为1080℃时,得到了综合性能比较好的NKNLS–3无铅压电陶瓷:ρ=4.29g/cm3,εr =826,tanδ=0.049,d33=190pC/N,kp=0.30。为了进一步提高材料的综合电性能,尤其是进一步提高材料的Qm,我们采用CuO和MnO2掺杂剂对NKNLS–3陶瓷进行改性研究。首先系统研究了CuO含量对NKNLS–3陶瓷显微结构和电性能的影响,结果表明:在CuO含量变化范围内,陶瓷相结构均以四方相相结构为主。随着CuO量的增加,εr下降,而Qm和tanδ先升高后降低。当CuO掺杂量为0.3mol%时的陶瓷样品具有较好的综合电性能。其次,系统研究了MnO2含量对NKNLS–3陶瓷显微结构和电性能的影响,结果表明:在MnO2含量变化范围内,陶瓷相结构均以四方相为主。随着MnO2含量的增加,εr和d33也均下降,kp变化不大,Qm先增加后降低,tanδ先降低后增加。当MnO2含量为0.15mol%时,陶瓷具有优良的综合电性能。更多还原

【Abstract】 Piezoelectric ceramics have been widely used for sensors, ultrasonic transducers and other electronic devices. Most of them are lead oxide–based piezoelectric ceramics, which contain more than 60 wt% lead. Lead is a very toxic substance, and the evaporation and contamination of toxic lead during the fabrication and disposal can cause a crucial environmental pollution. Therefore, it is necessary and urgency to develop lead–free piezoelectric ceramics to replace lead–based piezoelectric ceramics. (Na0.5K0.5)NbO3 (NKN) has been considered as a good candidate for lead–free piezoelectric ceramics due to its good piezoelectric properties. In this paper, 0.94(Na0.5K0.5)NbO3–xLiSbO3–yLiNbO3 (KNLNS) were prepared by the conventional mixed oxide route with normal sintering. The phase structure,piezoelectric and dielectric properties were investigated.0.94(Na0.5K0.5)NbO3–xLiSbO3–yLiNbO3 (NKNLS) ceramics were synthesized by traditional sintering process and effects of the LiSbO3 and LiNbO3 amounts on density, phase structure, microstructure and electric properties of NKNLS were investigated. X–ray diffraction (XRD) results showed that NKNLS can not form pure perovskite phase with excess LiNbO3 or LiSbO3 and the second phase K3Li2Nb5O15 with tetragonal tungsten bronze structure appeared, the pure perovskite phase only formed with proper amount of LiNbO3 and LiSbO3. Scanning electron microscope (SEM) observation indicated that the microstructure of NKNLS lead free ceramics exhibits apparent difference due to different amounts of LiSbO3 and LiNbO3. The 0.94(Na0.5K0.5)NbO3–xLiSbO3–yLiNbO3 lead free ceramics exhibits an excellent piezoelectric properties with x=0.03 and y=0.03. The effects of sintering temperature on the density, structure and electric properties of 0.94(Na0.5K0.5)NbO3–0.03LiSbO3–0.03LiNbO3(NKNLS–3) ceramics were also studied. XRD results showed that the crystal structure of the KNLNS ceramic were pure perovskite phase with tetragonal phase structure sintered at T≤1080℃, however, a K3Li2Nb5O15 phase with tetragonal tungsten bronze structure began to appear when the sintering temperature was higher than 1080℃. The optimum sintering temperature is 1080℃which was determined by measuring the density of the samples. SEM observation indicated that the sintering temperature had a great effect on the microstructure of the samples. The KNLNS–3 ceramics under the optimum sintering temperature showed excellent electric properties which as follows:ρ=4.29g/cm3,εr = 826, tanδ=0.049, d33 = 190pC/N, kp = 0.30. To further improve the electric properties of the ceramics, especially for Qm, KNLNS–3 ceramic was investigated by doping CuO and MnO2. The influence of CuO content on the phase structure, microstructure, dielectric and piezoelectric properties of the ceramics was investigated in detail. The XRD analysis results showed that all the ceramics were tetragonal phase. With the increasing of CuO content,εr kept decreasing all the time, Qm and tanδfirstly increased and then decreased. As CuO was 0.3mol%, the ceramics showed better electrical properties. The influence of MnO2 content on the phase structure, microstructure, dielectric and piezoelectric properties of the ceramics was also investigated in detail. The XRD analysis results showed that all the ceramics were tetragonal phase. With increasing the amount of MnO2,εr and d33 also decreased all the time, kp have little change. Qm increased at first and then decreased, whereas, tanδdecreased firstly, then increased. The ceramics with 0.15mol% MnO2 addition showed the optimized electrical properties.更多还原