【作者】 许春；

【导师】 张志力；

【作者基本信息】 北京交通大学 ， 材料学， 2008， 硕士

【摘要】 近年来，随着环境对材料无铅化的不断需求，新型功能材料包括微波介质材料、压电和铁电材料逐渐成为人们研究的热点。稀土铌酸系列陶瓷LnNbO₄（Ln代表La至Lu包含Y的稀土元素）属于类钙钛矿白钨矿结构（ABO₃），是一类结构和相变特性相似的新型微波介质陶瓷材料，其A位和B位离子可被半径和电价不同的各种元素离子在一定浓度范围内单独或复合取代，从而可以在比较大的范围内调节材料性能以适应不同场合的应用。本论文分别以重稀土元素镱（Yb）、轻稀土元素铈（Ce）为代表替代A位离子，结合前期合成制备的YNbO₄，研究这一系列陶瓷的制备工艺、显微结构与介电性能的关系等问题。以Yb₂O₃、Nb₂O₅为原料，按摩尔比Yb₂O₃：Nb₂O₅=1：1的比例在无保护气氛下氧化烧结，采用两种工艺——经预烧结后二次烧结和直接原位合成，对比得出了采用前者能烧结制得比较致密的陶瓷体，其中在136℃得到的YbNbO₄陶瓷的介电常数为23，品质因数Q值达到3．38x10⁴。以Bi₂O₃为助剂掺杂烧结YbNbO₄，从烧结温度、掺杂量方面研究了Bi₂O₃掺杂对YbNbO₄的烧结行为、相结构、显微形貌及其介电性能的影响。掺杂Bi₂O₃后，能一定程度降低YbNbO₄烧结温度，但对微波介电性能的影响不明显。以CeO₂、Nb₂O₅为原料，分别按摩尔比CeO₂：Nb₂O₅=1：1和CeO₂：Nb₂O₅=2：1的比例在无保护气氛下常压烧结，原位合成了铌酸铈陶瓷体，研究了其相结构随温度的转变(CeNbO_4+δ（δ=0～0．25）)、显微形貌和介电性能的特点。更多还原

【Abstract】 In recent years, with the increasing demand of lead-free and environmental materials, new types of communication function materials including dielectric, piezoelectric and ferroelectric materials are in the focus of people’s researches. Rare-earth niobate ceramics with general formula LnNbO₄（Ln represent La to Lu including Y） is a series of new functional microwave dielectric ceramic materials ,which has a ferroelastic phase of monoclinic structure at ambient temperature with similar structural phase transition characteristics, belongs to the perovskite scheelite class（ABO₃）. Their location of A or B can be replaced by other hydroniums with different radius and electrovalency to a certain extent, individually or in the compound. Thus, we can regulate the properties of material for different use. This paper is focus on replacing the location A with Yb or Ce, adding YNbO₄ synthesized before, preliminary study their synthesize technology, microscopic structure and dielectric properties of relations and so on.The main raw materials applied are ytterbium oxide （Yb₂O₃） and niobium oxide （Nb₂O₅）. YbNbO₄ were obtained with molar rate of Yb₂O₃:Nb₂O₅=1:1, sintering of non-protected atmosphere through two technics "pre-sintering and then second sintering" and "In-situ synthesis". We obtained YbNbO₄ ceramic with dielectric constant 26, Q value of 3.38×104 at sintering temperature 1360℃.Doped with Bi₂O₃, YbNbO₄ were studied on its sintering behavior, crystal structure and dielectric properties. The results showed that the sintering temperature is lowed to some extent, yet the influence of Bi₂O₃ to the dielectric properties is not very obvious.Next, using the cerium oxide （CeO₂） and niobium oxide （Nb₂O₅）, we got the ceramics of CeNbO_4+δ （δ=0-0.25） and some unknown phases with the molar rate of CeO₂ :Nb₂O₅=1:1 and CeO₂ :Nb₂O₅=2:1. CeNbO_4+δ is very sensitive to environmental oxygen. Their crystal transformation, microstructure and change of dielectric properties were investigated.更多还原