铌酸锶钡非充满型钨青铜陶瓷的结构与性能

发布时间：2018-03-04 07:11

本文选题：非充满型钨青铜　切入点：铁电相变　出处：《浙江大学》2015年硕士论文　论文类型：学位论文

【摘要】：(SrxBa1-x)Nb2O6陶瓷作为非充满型钨青铜结构的典型代表,由于优异的铁电、压电、热释电以及非线性光学性能,一直受到广泛关注。但对其介电性能、尤其是铁电相变与低温介电弛豫的认识仍有待加深。基于对充满型钨青铜陶瓷的最新研究,本文结合其结构演化,对(SrxBa1-x)Nb2O6陶瓷的介电性能、铁电相变进行了深入研究。(SrxBa1-x)Nb2O6的介电和铁电性能随着x而变化,其中A1/A2离子占位作为主要因素决定着变化的趋势。当Sr/Ba摩尔比接近1：4比值(此时,离子半径较大的Ba离子占据4个A2位,离子半径相对小的Sr离子占据1个A1位,另一个A1位空缺),(SrxBa1-x)Nb2O6将呈现正常铁电体特性,在tanδ-T图中只出现一个介电异常(x=0.25)。而当Sr/Ba摩尔比远离1：4比值时,(SrxBa1-x)Nb2O6将呈现典型的弛豫铁电特性,在tenδ-T图中出现三个介电异常(x=0.75)。其中,非公度氧八面体倾斜和A位离子的无序分布是其出现弛豫铁电性和低温介电弛豫的结构起源。(SrxBa1-x)Nb2O6陶瓷的铁电畴结构进一步证实了其随着x增加从正常铁电体到弛豫铁电体的演化。较低电场下的电滞回线(P-E)随温度的变化显示,最大极化值(Pmax)和剩余极化值(Pr)在低温下出现下降甚至几乎为零,电滞回线出现线性响应。这一现象的出现主要是因为低温下矫顽场的增加,而非再入弛豫。当电场增加到足够高时,所有组分在低温下都得到饱和的非线性电滞回线。
[Abstract]:As a typical representative of non-filled tungsten bronze structure, SrxBa1-xNb2O6 ceramics have been widely concerned because of their excellent ferroelectric, piezoelectric, pyroelectric and nonlinear optical properties. In particular, the understanding of ferroelectric phase transition and low-temperature dielectric relaxation still needs to be deepened. Based on the latest research on the filled tungsten bronze ceramics, the dielectric properties of SrxBa1-xNb2O6 ceramics have been studied in this paper in combination with their structural evolution. The dielectric and ferroelectric properties of SrxBa1-xNb2O6 vary with x, in which A 1 / A2 ion occupation is the main factor determining the change trend. When the molar ratio of Sr/Ba is close to 1: 4, The Ba ion with larger ion radius occupies 4 A2 sites, the Sr ion with relatively small ion radius occupies 1 A1 site, and the other Al vacancy position SrxBa1-xNb2O6 exhibits normal ferroelectric properties. There is only one dielectric anomaly in the tan 未 -T diagram, and when the Sr/Ba molar ratio is far from the ratio of 1: 4, SrxBa1-xNb2O6 will exhibit typical relaxor ferroelectric properties, and three dielectric anomalies will appear in the ten 未 -T diagram. Incommensurate oxygen octahedron tilt and disordered distribution of A-site ions are the structural origin of relaxation ferroelectrics and low-temperature dielectric relaxation. The ferroelectric domain structure of SrxBa1-xNb2O6 ceramics further confirms that the ferroelectric structure changes from normal ferroelectrics to relaxation with the increase of x. Evolution of ferroelectrics. The changes of hysteresis loop P-E) at lower electric field show that, The maximum polarization value Pmax) and the residual polarization value Pr) decreased to almost zero at low temperature, and the hysteresis loop showed a linear response, which was mainly due to the increase of coercive field at low temperature. When the electric field is high enough, the saturated nonlinear hysteresis loop is obtained at low temperature.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.1

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