【作者】 钮效鹍；

【导师】 张家良；

【作者基本信息】 山东大学 ， 材料物理与化学， 2008， 硕士

【摘要】 由于铅对人体和环境的危害性，铅含量很高的传统的铅基压电陶瓷的应用受到极大挑战。因此，发展无铅系环境协调性压电陶瓷成为一项紧迫且具有重大实用意义的课题。本论文利用传统固相反应法制备了(K_xNa_1-x)_1-yLi_yNbO₃和Sr_2-xCa_xNaNb₅O₁₅（分别简写为KNLN和SCNN）两种体系的无铅压电陶瓷，系统地研究了其微观形貌、结晶结构、介电和压电等方面的物理性质。（K,Na）NbO₃基陶瓷（KNN）以其优异的压电性能成为目前无铅压电陶瓷材料的研究热点。近年对KNN基压电陶瓷的研究，主要集中在这两个方面：（1）探索具有更优异压电性能的KNN基陶瓷组分；（2）研究引起KNN基陶瓷呈现优异压电性能的物理机制，如准同型相界、晶体结构相变等。本论文中关于(K_Na_1-x)_1-yLi_yNbO₃体系压电陶瓷的研究侧重于对晶体结构随组分变化的规律性和晶体结构相变对压电性能的影响方面。对于(K_0．50Na_0．50)_1-yLi_yNbO₃（y=0-0．08）压电陶瓷的研究，证实了文献报道的晶体结构和压电性能随组分变化的结果。对于(K_xNa_1-x)_0．94Li_0．06NbO₃（X=0．30-0．70）压电陶瓷的研究，发现了晶体结构随着组分x变化发生正交-四方-正交的变化，相界分别位于x=0．40和x=0．60处。在所研究的(K_xNa_1-x)_1-yLi_yNbO₃陶瓷体系中，两种组分分别为(K_0．50Na_0.50)_0．935Li_0．065NbO₃和(K_0．45Na_0．55)_0．94Li_0．06NbO₃的陶瓷样品呈现出比较优异的压电性能(d₃₃>200pC／N，k_p>45％)。由介电温谱测量得到的这两种组分的陶瓷样品的正交-四方晶体结构相变温度分别为27℃和35℃。推测它们的良好压电性能应与在室温附近发生的正交-四方相变有着密切的关联性。本论文中制备的钨青铜结构Sr_2-xCa_xNaNb₅O₁₅（x=0-0．15）无铅压电陶瓷的d₃₃为70pC／N左右，室温介电常数大于1400，室温介电损耗小于1％，相对密度大于92％。当Ca²⁺的添加量x超过0．15时，相对密度、平均晶粒尺寸和压电性能均开始降低。组分为x=0．10的Sr_1．9Ca_0．1NaNb₅O₁₅陶瓷具有良好的压电性能(d₃₃=74pC／N，k_p=8．2％，Q_m=923)，具有一定应用价值。更多还原

【Abstract】 The application of traditional lead-based piezoelectric ceramics which contain high lead are strongly challenged because the lead can cause serious damage to human and environment. As a result, the development of lead-free and environmentally-friendly piezoelectric ceramics becomes an urgent and of great practical significance task. In this paper, two type of lead-free piezoelectric ceramics of (K_xNa_1-x)_1-yLi_yNbO₃ and Sr_2-xCa_x NaNb₅O₁₅（abbreviated to KNLN and SCNN, respectively） were fabricated by solid-state reaction technique. Microstructure, crystallographic stucture, dielectric and piezoelectric properties of those two type of ceramics were investigated systematically.The （K,Na）NbO₃ （KNN） based ceramics have been paid much attention because of their enhanced piezoelectric properties. At present, the investigation on KNN-based ceramics is concentrated on two aspects, （1） exploring the KNN-based compositions with more enhanced piezoelectric properties, and （2） researching on factors which improve the piezoelectric properties of KNN-based ceramics, such as morphotropic phase boundary （MPB） and polymorphic phase transition.In first part of this paper, the variety of polymorphic structural phase transition（PPT） and the influence of PPT to the piezoelectric properties were mainly discussed. In (K_0.50Na_0.50)_1-yLi_yNbO₃ （y=0-0.08） ceramics, with the increase of Li content y the experimental result of PPT and the piezoelectric properties are generally in agreement with that in previous literature. In (K_xNa_1-x)_0.94Li_0.06NbO₃（x=0.30-0. 70） ceramics, with the increase of K content x it exists an orthorhombic-tetragonal- orthorhombic phase transition and the phase boundaries are located at x=0.40 and x=0.60, respectively. Two ceramic samples of (K_0.50Na_0.50)_0.935Li_0.065NbO₃ and (K_0.45Na_0.55)_0.94Li_0.06NbO₃ show the best piezoelectric properties of d₃₃>200pC/N and k_p>45%. The orthorhombic-tetragonal phase transition temperatures of these two samples are 27℃and 35℃, respectively. It can be speculated that the nice piezoelectric properties of those two samples are mainly related to the existence of orthorhombic-tetragonal phase transition at room temperature.In second part of this paper, the Sr_2-xCa_xNaNb₅O₁₅ piezoelectric ceramics with tungsten bronze structure show the piezoelectric properties of d₃₃-70pC/N, dielectric constantε₁>1400, dielectric loss tgδ<1% and relatice densityρ>92%. For SCNN ceramics, the relative density, the average grain size and the piezoelectric properties begin to decrease when the Ca²⁺ content exceeds 0.15. The ceramic sample of Sr_1.9Ca_0.1NaNb₅O₁₅ reveals the better piezoelectric properties of d₃₃=74pC/N, k_p=8.2% and Q_m=923.更多还原