铋基钙钛矿结构材料的制备与电学性能研究

发布时间：2018-07-22 19:55

【摘要】：铋基钙钛矿结构电子材料由于其独特的介电、铁电、压电等方面的性能而备受关注,其中,铁酸铋(BiFeO_3,BFO)是唯一室温下同时具有铁电序和反铁磁序的多铁材料,表现出良好的电磁学特性、半导体特性、阻变特性和气敏性能等;此外,钛酸铋钠(Bi_(0.5)Na_(0.5)TiO_3,BNT)则是一种具有优良压电性能的材料,通过与钛酸铋钾(Bi0.5K0.5TiO3,BKT)等按一定比例复合,在构成准同型相界(MPB)基础上改性,会表现出高的电致应变性能和优良的介电调谐性能等。因此,本论文以BiFeO_3和Bi_(0.5)Na_(0.5)TiO_3基材料为研究对象,采用固相反应法、溶胶凝胶法和水热法等方法,对其进行A位离子取代或复合改性,并研究了取代复合对其铁电、压电、介电调谐、电致应变以及气敏等性能的影响规律。采用固相反应法制备了A位La取代的BiFeO_3(Bi1-xLaxFeO3,BLF)陶瓷,研究取代比例对其电学非线性的影响。在不同气氛下对BLF进行热处理并测试分析电学性能,发现BLF电导机制属于p型空穴导电机制,热处理气氛的氧分压越高导电性越好。BLF存在非线性伏安特性,当外电场超过一定阈值之后,电流大幅增加,电阻明显减小,非线性系数随La取代量的减少而增加,随温度的升高而增加,随热处理气氛氧分压的增加而增加,经过氧气退火处理的BLF非线性系数最高。指出这种阻变效应来源于其铁电畴与畴壁处的微观电子异质结构,铁电畴与畴壁的导电性存在差异而导致畴壁处存在整流效应。采用溶胶凝胶法制备了A位Ba取代的BiFeO_3(Bi0.9Ba0.1FeO2.95,BBFO10)粉体,研究了其对几种典型挥发性气体的气敏性能。BBFO10比纯BFO的气体探测灵敏度有大幅提高,并具有快速的响应恢复速度、良好的气体选择性和长期稳定性。实验得出由于BBFO10比BFO粉体的比表面积大,在气敏反应过程中与气体分子接触吸附的面积增大,有利于提高反应敏感度。另外由于二价Ba2+离子部分取代三价Bi3+离子,使得BBFO10中氧空位浓度增加,也有利于提高BBFO10的气敏性能。采用水热法和微波水热法制备了BiFeO_3和A位Ce取代的BiFeO_3(Bi0.9Ce0.1FeO3,BCFO)粉体,研究了其磁学特性。微波水热法制备的BFO表现出顺磁性,而水热法制备的BFO和BCFO-H表现为弱铁磁性,Ce的部分取代明显提高了BCFO的磁学性能,这是由于内外层轨道杂化电子迁移以及离子半径的差异使BFO的螺旋调制结构发生变化而导致。制备了(1-x)(0.8BNT-0.2BKT)-xNaNbO3(BNKT-xNN)陶瓷,研究了其应变、铁电和介电性能随组分和温度的变化规律。结果表明,随着NN含量的增加,BNKT-xNN逐渐从非遍历性弛豫铁电体转变为遍历性弛豫体,表现为铁电相-弛豫相转变温度TF-R从室温以上逐渐降至室温以下,压电系数d33大幅下降,电滞回线从饱和回线变成瘦腰状,应变S-E曲线由蝴蝶形转变为芽形。非遍历性弛豫体组分在电场作用下发生不可逆相变,从赝立方相转变三方相,升温至TF-R温度以上应变大幅增加。属于遍历性弛豫体组分的BNKT-0.04NN在室温下的电致应变0.445%、Smax/Emax值可达810 pm/V,大应变来源于电场激发的遍历性弛豫相与铁电相之间可逆相变。研究了BNKT-xNN陶瓷的介电调谐性能、热释电性能及导电机制,材料均表现出显著的介电非线性调谐性能,且随着NN含量的不同其介电调谐行为表现不同,作为非遍历弛豫体的组分在场致相变前后介电调谐行为由非线性转变为线性关系,遍历性弛豫体的组分则始终保持非线性关系。BNKT-xNN的导电机制属于n型电子导电机制,其电导率随热处理氧分压浓度的降低而增加,其电导激活能随热处理氧分压浓度的降低而降低。研究了(1-x)(0.8BNT-0.2BKT)-xBiMg2/3Nb1/3O3(BNKT-xBMN)陶瓷的应变、铁电和介电性能随组分和温度的变化规律。BNKT-x BMN的物相为赝立方相,作为非遍历性弛豫铁电体的BNKT-0BMN在室温下表现为典型的铁电体特征,在电场作用下发生不可逆相变。BNKT-0.02BMN为遍历性弛豫铁电体,电致应变值可达0.431%,在较低的电场强度40 kV/cm下,Smax/Emax即可高达862 pm/V,具有较高的场致应变效率,因而适合实际应用。
[Abstract]:Bismuth based perovskite structure electronic materials have attracted much attention due to their unique dielectric, ferroelectric and piezoelectric properties. BiFeO_3 (BFO) is the only ferroelectric and antiferromagnetic material at the same time at room temperature. It shows good electromagnetics, semiconductor properties, resistance and gas sensitivity. In addition, titanic acid Sodium bismuth (Bi_ (0.5) (0.5) Na_ (0.5) TiO_3, BNT) is a kind of material with excellent piezoelectric properties. By combining with potassium bismuth titanate (Bi0.5K0.5TiO3, BKT) in a certain proportion and on the basis of the quasi Homo phase boundary (MPB), it will show high electrostrain properties and excellent dielectric tuning properties. Therefore, this paper is based on BiFeO_3 and Bi_ (0.5) Na_. (0.5) TiO_3 based material was used as the research object. By solid phase reaction, sol-gel method and hydrothermal method, A bit ion substitution or compound modification was carried out, and the effects of substitution composite on its ferroelectric, piezoelectricity, dielectric tuning, electrostrain and gas sensitivity were studied. The BiFeO_3 (Bi) of A position La substitution was prepared by the solid state reaction method. 1-xLaxFeO3, BLF) ceramics, study the effect of the substitution ratio on its electrical nonlinearity. Heat treatment and test the electrical properties of BLF under different atmospheres. It is found that the BLF conductance mechanism belongs to the P cavity conduction mechanism. The higher the oxygen partial pressure in the heat treatment atmosphere is, the better the conductivity is, the better the.BLF is in the nonlinear volt ampere characteristic, when the external electric field exceeds a certain threshold. After the increase of the current and the decrease of the resistance, the nonlinear coefficient increases with the decrease of the La substitution, increases with the increase of the temperature, and increases with the increase of the oxygen partial pressure in the heat treatment atmosphere. The nonlinear coefficient of the annealing treatment is the highest. It is pointed out that this resistance effect comes from the micro electronic heterogeneity at the ferroelectric domain and the domain wall. Structure, the conductivity of ferroelectric domain and domain wall is different, which leads to the existence of rectifying effect at the domain wall. The BiFeO_3 (Bi0.9Ba0.1FeO2.95, BBFO10) powder, which is substituted by A bit Ba, is prepared by sol-gel method. The gas sensing performance of several typical volatile gases is investigated and the sensitivity of the gas detection is significantly higher than that of pure BFO, and it is fast and fast. The response recovery speed, good gas selectivity and long-term stability are obtained. It is found that the area of BBFO10 is larger than the BFO powder, and the area of the contact with the gas molecules increases in the gas sensitive reaction. It is beneficial to increase the sensitivity of the reaction. In addition, the two valence Ba2+ ion division is used to replace the trivalent Bi3+ ion, which makes the oxygen vacancy in BBFO10. The increase in concentration also helps to improve the gas sensitivity of BBFO10. The BiFeO_3 (Bi0.9Ce0.1FeO3, BCFO) powders of BiFeO_3 and A sites were prepared by hydrothermal method and microwave hydrothermal method. The magnetic properties of the BiFeO_3 (Bi0.9Ce0.1FeO3, BCFO) powders were studied. The BFO prepared by the microwave hydrothermal method showed paramagnetic, while the BFO and BCFO-H prepared by hydrothermal method were weak ferromagnetic and Ce partly replaced. The magnetic properties of BCFO are obviously improved. This is due to the variation of the hybrid electron migration and the difference in the ionic radius of the internal and external orbit. The (1-x) (0.8BNT-0.2BKT) -xNaNbO3 (BNKT-xNN) ceramics are prepared. The changes of the strain, ferroelectric and dielectric properties with the components and temperature are studied. With the increase of NN content, BNKT-xNN gradually transforms from non ergodic relaxor ferroelectrics to ergodical relaxor, which shows that the phase transition temperature of ferroelectric phase TF-R decreases from room temperature to room temperature, and the piezoelectric coefficient d33 drops sharply, the hysteresis loop becomes thin waist, and the strain S-E curve is transformed from butterfly shape to bud shape. The irreversible phase transition of the ergodical relaxor component occurs under the action of the electric field. The transformation of the three square phase from the pseudopotential phase to the temperature above TF-R increases significantly. The electrostrain of the BNKT-0.04NN at room temperature is 0.445%, the Smax/Emax value is up to 810 pm/V, and the large strain is derived from the ergodical relaxation phase excited by the electric field. The dielectric tuning properties, the pyroelectric properties and the conduction mechanism of BNKT-xNN ceramics have been studied. The dielectric tuning properties of the materials are significant, and the dielectric tuning behavior is different with the different NN content, and the dielectric tuning behavior of the non ergodic relaxor components before and after the presence of the phase transition is not. The linear transformation is linear, and the group principle of ergodicity relaxor always maintains the nonlinear relation of the nonlinear relation.BNKT-xNN, which is n electron conduction mechanism, and its conductivity increases with the decrease of the concentration of oxygen partial pressure in heat treatment, and its conductance activation energy decreases with the decrease of the concentration of oxygen partial pressure in heat treatment. (1-x) (0.8BNT-0.2BKT) -xBiMg2/3N The strain, ferroelectric and dielectric properties of b1/3O3 (BNKT-xBMN) ceramics vary with the composition and temperature. The phase of.BNKT-x BMN is pseudopotential phase. As a non ergodical relaxor ferroelectric body, BNKT-0BMN exhibits a typical ferroelectric characteristic at room temperature. The irreversible phase transition.BNKT-0.02BMN is a ergodical relaxor ferroelectrics under the action of the electric field. The strain rate can reach 0.431%. Under the low electric field intensity of 40 kV/cm, Smax/Emax can reach up to 862 pm/V and has higher field strain efficiency, so it is suitable for practical application.
【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ174.1;TB34

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