铋基钙钛矿弛豫铁电陶瓷的组成设计、机电性能及机理研究
发布时间：2018-07-15 14:38
【摘要】：随着在(Na0.5Bi0.5)TiO3 (BNT)体系以及其它铋基钙钛矿体系中大的电致应变现象的发现,铋基钙钛矿体系应变性能的研究逐渐成为近年来的研究热点。然而,目前铋基钙钛矿体系的研究还存在诸多问题：如已有的研究主要针对BNT-BaTiO3/(K0.5Bi0.5)TiO3 (BT/KBT)二元体系或以此为基体制备的三元体系展开,对其它BNT体系或其它铋基钙钛矿体系的研究相对较少；这些体系只能在较高的电场下才能获得大应变；这些体系中获得的应变都具有明显的组成和温度依赖特性以及较大的应变滞后；铋基钙钛矿体系大应变的产生机理及应变产生的具体过程还不是很清楚等等。针对上述问题,本论文主要选取不同的铋基钙钛矿体系进行对比研究及相应的组成优化设计,显著地改善了上述铋基钙钛矿体系应变性能的不足,获得了具有优异应变特性的铋基钙钛矿陶瓷；基于多种测试手段,深入研究了不同体系中组成、结构、性能之间的相互关系,对铋基钙钛矿体系大应变的产生机理及应变性能的调节机理作了进一步深入研究。全文主要研究内容如下：(1)在BNT-PbTiO3基础之上,利用Bi(Mg0.5Ti0.5)O3取代BNT,研究了BNT-PbTiO3-xBi(Mg0.5Ti0.5)O3 (BNT-PT-xBMT)三元体系的相结构及电学性能的变化。研究发现,随BMT含量的增加,该体系的相结构由菱方-四方相共存(x0.18)转变为伪立方相(x≥0.18),并且这一过程伴随着铁电-非各态历经-各态历经弛豫相的转变,从而在非各态历经与各态历经弛豫相共存处(x=0.20-0.22)获得了大的电致应变：7 kV/mm电场下获得的应变为0.45%。对于x0.12组成,介温测试出现的两个具有不同性质的介电异常分别与菱方相和四方相到弛豫相的转变有关。通过同步辐射X射线衍射研究进一步发现,x0.18组成在极化后均出现了明显的电畴取向。随温度升高,x0.12组成中的菱方相首先出现取向程度的减弱,四方相电畴的取向能维持到更高温度,随BMT含量增加,四方相电畴的稳定性逐渐减弱,在更低的温度出现取向程度的减弱。见第二章。(2)结合BMT-PT和BNT两个体系的特点构建了新的BMT基三元体系BMT-PT-BNT,成功的实现了对应变性能的有效调节。研究发现,在该体系中通过进行不同的组成设计均能够有效调节其介电弛豫特性并在各态历经与非各态历经弛豫相共存附近获得大的电致应变：7 kV/mm电场下获得的应变为0.41-0.43%。通过原位电场作用下同步辐射X射线衍射研究表明,该体系大应变的产生与电场诱发的弛豫-铁电转变有关。同时,由于0.45BMT-PT-0.32BNT组成的极性纳米微区和畴壁均能对电场做出快速响应,使得其应变表现出频率不敏感特性。此外,通过对相界附近具有伪立方相和四方相共存组成的研究表明,决定其压电及应变性能的原因除与两相共存有关外,伪立方相和四方相各自的特性及其相对含量对电学性能同样具有显著的影响。见第三章。(3)利用Pb(Mg1/3Nb2/3)03(PMN)对BMT-PT体系进行改性,首次在 BMT-PT-PMN体系中获得了具有较好的组成不敏感的大应变(BMT-0.3PT-xPMN体系在0.2x0.5范围内7 kV/mm电场下获得的应变为～0.40%)、温度不敏感的大应变(BMT-0.3PT-0.20PMN组成在室温-160 ℃范围内5 kV/mm电场下获得的应变为～0.30%±10%)以及具有较小应变滞后的大应变(BMT-0.3PT-0.45PMN组成在7 kV/mm电场下获得的应变为0.42%,应变滞后为～23%),使得该体系有望成为一种很有潜力的驱动器用陶瓷材料。利用同步辐射X射线衍射并结合其它测试手段,研究了该体系中大应变的产生机理及应变性能改善的机理。研究发现,该体系大应变的产生与电场诱发的弛豫-铁电转变有关,并且转变过程中中间相的出现能够显著降低应变的滞后。应变的温度不敏感特性与富BMT组成特殊的畴结构有关,导致该体系的铁电-弛豫转变温度与冻结温度之间存在较大的差距,因此能够在较宽的温度区间内获得非各态历经与各态历经弛豫相共存。此外,不同电场下相结构随温度变化的稳定性及应变形成机制的不同对应变温度稳定性也有明显影响。同时,这一特殊畴结构也使得该体系在较宽的组成区间内能够出现非各态历经与各态历经弛豫相共存,获得组成不敏感的大应变。这一研究为铋基钙钛矿体系应变性能的改善提供了一种新的组成设计思路。见第四章。(4)利用PMN取代BiFe03,首次在BiFe03-PbTi03-xPMN(BF-PT-xPMN)体系中实现了低电场诱导产生大的电致应变,显著地提高了这一类材料的动态d33*：x=0.35组成在2.5-7 kV/mm电场区间内应变为～0.22-0.55%,并且在3.5 kV/mm电场下获得了最大的动态d33'=～1100 pm/V,对于材料的实际应用具有重要价值。同时,在富PMN一侧获得了具有较小应变滞后的大应变：x=0.68组成在5 kV/mm电场下获得的应变为～0.33%,应变滞后为～25%。通过对不同组成在升降电场过程中相结构变化的研究发现,该体系中大应变的产生与电场诱发的弛豫-铁电转变(极性纳米微区的长大)、菱方相电畴的翻转以及菱方-四方相变有关。其中,菱方相电畴翻转对电致应变产生的额外贡献对该体系应变性能的提高具有重要的作用。见第五章。(5)通过系统分析不同铋基钙钛矿体系中电致应变与结构之间的关系,对铋基钙钛矿体系产生大应变的机理及应变性能改善的机理作了进一步研究。首先,我们首次明确了电场诱发的弛豫-铁电可逆转变过程的本质是材料中极性纳米微区在电场作用下的长大,以及随后的电畴翻转及铁电相变,并对铋基钙钛矿体系在电场作用下的电畴演变过程进行了总结。其次,我们揭示了升降电场过程中相变过程的不对称性是导致铋基钙钛矿弛豫铁电体系应变滞后的主要原因,进而通过组成优化设计达到了减小应变滞后的目的。通过微观结构的分析我们认为,在加载电场的周期过程中相变过程不对称现象的出现与化学有序区在电场作用下的运动以及在铁电畴畴壁处的富集有关。见第六章。
[Abstract]:With the discovery of large electrostrain phenomena in the (Na0.5Bi0.5) TiO3 (BNT) system and other bismuth perovskite systems, the study of the strain properties of the bismuth perovskite system has gradually become a research hotspot in recent years. However, there are many problems in the study of the bismuth perovskite system: for example, the existing research is mainly aimed at BNT-BaTiO3/ (K0.5 Bi0.5) the TiO3 (BT/KBT) two element system or the three element system prepared as a matrix, is relatively less studied for other BNT systems or other bismuth based perovskite systems; these systems can only obtain large strains at a higher electric field; the strains obtained in these systems have obvious composition and temperature dependence and larger. The strain generation mechanism of bismuth based perovskite system and the specific process of strain production are not very clear. In this paper, a comparative study of different bismuth based perovskite systems and the corresponding optimization design have been made in this paper, and the strain performance of the bismuth based perovskite system has been greatly improved. The bismuth based perovskite ceramics with excellent strain characteristics were obtained. Based on various testing methods, the relationship between the composition, structure and properties of different systems was deeply studied. The mechanism of large strain production of bismuth perovskite system and the adjustment mechanism of strain properties were further studied. The main contents of the full text are as follows. (1) (1) on the basis of BNT-PbTiO3, using Bi (Mg0.5Ti0.5) O3 to replace BNT, the phase structure and electrical properties of BNT-PbTiO3-xBi (Mg0.5Ti0.5) O3 (BNT-PT-xBMT) three element system are studied. It is found that the phase structure of the system is changed from rhomboid tetragonal phase to pseudo cubic phase (x > 0.18) with the increase of BMT content. The process is accompanied by the transition of the ferroelectric - non state - all States - the relaxation phase of each state, thus the large electroinduced strain is obtained in the non state period of the coexistence of the relaxation phase (x=0.20-0.22) in each state. The strain obtained under the 7 kV/mm electric field is 0.45%. for the x0.12, and the dielectric anomalies of the dielectric temperature test are different from the diamond, respectively. The square phase and the Quartet phase are related to the transition of the relaxation phase. Through the study of synchrotron radiation X ray diffraction, it is found that the x0.18 composition appears obvious domain orientation after polarization. As the temperature rises, the diamond square phase in the x0.12 composition decreases first, and the orientation of the Quartet phase domain can be maintained to a higher temperature, with the increase of the content of the BMT. The stability of the Quartet phase domain gradually weakened and the degree of orientation decreased at a lower temperature. See second chapter. (2) a new BMT based three element system BMT-PT-BNT was constructed in combination with the characteristics of the two systems of BMT-PT and BNT, which successfully realized the effective adjustment of the strain performance. The dielectric relaxation characteristics can be effectively regulated and large electroinduced strain is obtained near the coexistence of the relaxation phase in each state. The strain obtained under the 7 kV/mm electric field is 0.41-0.43%. through the synchronous radiation X ray diffraction study under the action of the in situ electric field, which shows that the large strain of the system and the relaxation ferroelectric transition induced by the electric field At the same time, due to the rapid response of the polar nanoscale and domain walls composed of 0.45BMT-PT-0.32BNT to the electric field, the strain shows a frequency insensitivity. In addition, a study of the coexistence of pseudo cubic and tetragonal phase in the vicinity of the phase boundary shows that the reasons for determining its piezoelectric and strain properties are coexisting with the two phases. In addition, the characteristics and relative content of the pseudbocube and tetragonal phase have a significant influence on the electrical properties. See the third chapter. (3) using Pb (Mg1/3Nb2/3) 03 (PMN) to modify the BMT-PT system, the large strain with a better composition insensitive (BMT-0.3PT-xPMN system in the 0.2x0.5 range) is obtained for the first time in the BMT-PT-PMN system. The strain obtained under the internal 7 kV/mm electric field is 0.40%), the large strain which is insensitive to temperature (the strain obtained by the BMT-0.3PT-0.20PMN in the 5 kV/mm electric field within the range of -160 C at room temperature is 0.30% + 10%) and a large strain with a smaller strain lag (the strain of the BMT-0.3PT-0.45PMN composition under 7 kV/ mm electric field is 0.42%, and the strain lag is 2). 23%) the system is expected to be a promising ceramic material for actuators. Synchrotron radiation X ray diffraction and other testing methods have been used to study the mechanism of large strain production and the mechanism of strain performance improvement in the system. The study shows that the large strain of the system is related to the relaxation ferroelectric transition induced by electric field, The occurrence of the mesophase in the transition process can significantly reduce the lag of the strain. The temperature insensitivity of the strain is related to the special domain structure of the rich BMT, which leads to a large gap between the ferroelectric relaxation transition temperature and the freezing temperature of the system, so it can be obtained in the wider range of temperature range and in the different states and states. In addition, the phase structure under different electric fields has an obvious influence on the stability of the temperature change and the different strain formation mechanism corresponding to the temperature stability. At the same time, this special domain structure can also make the system coexist with each state of the relaxation phase in the wider range of composition, and the composition of the system can be obtained. Sensitive large strain. This study provides a new design idea for the improvement of the strain performance of the bismuth perovskite system. See Chapter fourth. (4) using PMN to replace BiFe03 for the first time in the BiFe03-PbTi03-xPMN (BF-PT-xPMN) system, a low electric field is induced to produce a large electroinduced strain and a significant increase in the dynamic d33* of this kind of material. The composition of x=0.35 should be changed to 0.22-0.55% in the 2.5-7 kV/mm electric field interval, and the maximum dynamic d33'= ~ 1100 pm/V is obtained under the 3.5 kV/mm electric field. It is of great value for the practical application of the material. At the same time, the large strain with a smaller strain lag is obtained on the rich PMN side: the strain obtained by the x=0.68 composition in the 5 kV/mm electric field. For 0.33%, the strain lag is to 25%. through the study of the phase structure change of the different composition in the process of the electric field. It is found that the generation of large strain in the system is related to the relaxation ferroelectric transition (the growth of the polar nanoscale micro area) induced by the electric field, the reversal of the rhombus phase domain and the rhombus tetragonal phase transition. The additional contribution of strain generation plays an important role in improving the strain performance of the system. See fifth chapters. (5) through systematic analysis of the relationship between the electrostrain and structure of different bismuth perovskite systems, the mechanism of producing large strain and improving the strain performance of bismuth based perovskite system are further studied. First, we For the first time, it is clear that the essence of the relaxation ferroelectric reversible transformation process induced by the electric field is the growth of polar nanometers in the material under the action of the electric field, and the subsequent electric domain inversion and ferroelectric phase transition, and the evolution process of the domain of the bismuth perovskite system under the action of the electric field. Secondly, we reveal the phase in the process of the elevating electric field. The asymmetry of the changing process is the main cause of the strain lag in the relaxation ferroelectric system of the bismuth based perovskite, and then the purpose of reducing the strain lag is achieved through the composition optimization design. Through the analysis of the microstructure, we think that the asymmetric phenomenon of the phase transition process and the chemical ordered area are in the electric field during the period of the loading of the electric field. The motion and the enrichment at the domain walls of ferroelectric domains are described in the sixth chapter.
【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ174.1
本文编号：2124405
[Abstract]:With the discovery of large electrostrain phenomena in the (Na0.5Bi0.5) TiO3 (BNT) system and other bismuth perovskite systems, the study of the strain properties of the bismuth perovskite system has gradually become a research hotspot in recent years. However, there are many problems in the study of the bismuth perovskite system: for example, the existing research is mainly aimed at BNT-BaTiO3/ (K0.5 Bi0.5) the TiO3 (BT/KBT) two element system or the three element system prepared as a matrix, is relatively less studied for other BNT systems or other bismuth based perovskite systems; these systems can only obtain large strains at a higher electric field; the strains obtained in these systems have obvious composition and temperature dependence and larger. The strain generation mechanism of bismuth based perovskite system and the specific process of strain production are not very clear. In this paper, a comparative study of different bismuth based perovskite systems and the corresponding optimization design have been made in this paper, and the strain performance of the bismuth based perovskite system has been greatly improved. The bismuth based perovskite ceramics with excellent strain characteristics were obtained. Based on various testing methods, the relationship between the composition, structure and properties of different systems was deeply studied. The mechanism of large strain production of bismuth perovskite system and the adjustment mechanism of strain properties were further studied. The main contents of the full text are as follows. (1) (1) on the basis of BNT-PbTiO3, using Bi (Mg0.5Ti0.5) O3 to replace BNT, the phase structure and electrical properties of BNT-PbTiO3-xBi (Mg0.5Ti0.5) O3 (BNT-PT-xBMT) three element system are studied. It is found that the phase structure of the system is changed from rhomboid tetragonal phase to pseudo cubic phase (x > 0.18) with the increase of BMT content. The process is accompanied by the transition of the ferroelectric - non state - all States - the relaxation phase of each state, thus the large electroinduced strain is obtained in the non state period of the coexistence of the relaxation phase (x=0.20-0.22) in each state. The strain obtained under the 7 kV/mm electric field is 0.45%. for the x0.12, and the dielectric anomalies of the dielectric temperature test are different from the diamond, respectively. The square phase and the Quartet phase are related to the transition of the relaxation phase. Through the study of synchrotron radiation X ray diffraction, it is found that the x0.18 composition appears obvious domain orientation after polarization. As the temperature rises, the diamond square phase in the x0.12 composition decreases first, and the orientation of the Quartet phase domain can be maintained to a higher temperature, with the increase of the content of the BMT. The stability of the Quartet phase domain gradually weakened and the degree of orientation decreased at a lower temperature. See second chapter. (2) a new BMT based three element system BMT-PT-BNT was constructed in combination with the characteristics of the two systems of BMT-PT and BNT, which successfully realized the effective adjustment of the strain performance. The dielectric relaxation characteristics can be effectively regulated and large electroinduced strain is obtained near the coexistence of the relaxation phase in each state. The strain obtained under the 7 kV/mm electric field is 0.41-0.43%. through the synchronous radiation X ray diffraction study under the action of the in situ electric field, which shows that the large strain of the system and the relaxation ferroelectric transition induced by the electric field At the same time, due to the rapid response of the polar nanoscale and domain walls composed of 0.45BMT-PT-0.32BNT to the electric field, the strain shows a frequency insensitivity. In addition, a study of the coexistence of pseudo cubic and tetragonal phase in the vicinity of the phase boundary shows that the reasons for determining its piezoelectric and strain properties are coexisting with the two phases. In addition, the characteristics and relative content of the pseudbocube and tetragonal phase have a significant influence on the electrical properties. See the third chapter. (3) using Pb (Mg1/3Nb2/3) 03 (PMN) to modify the BMT-PT system, the large strain with a better composition insensitive (BMT-0.3PT-xPMN system in the 0.2x0.5 range) is obtained for the first time in the BMT-PT-PMN system. The strain obtained under the internal 7 kV/mm electric field is 0.40%), the large strain which is insensitive to temperature (the strain obtained by the BMT-0.3PT-0.20PMN in the 5 kV/mm electric field within the range of -160 C at room temperature is 0.30% + 10%) and a large strain with a smaller strain lag (the strain of the BMT-0.3PT-0.45PMN composition under 7 kV/ mm electric field is 0.42%, and the strain lag is 2). 23%) the system is expected to be a promising ceramic material for actuators. Synchrotron radiation X ray diffraction and other testing methods have been used to study the mechanism of large strain production and the mechanism of strain performance improvement in the system. The study shows that the large strain of the system is related to the relaxation ferroelectric transition induced by electric field, The occurrence of the mesophase in the transition process can significantly reduce the lag of the strain. The temperature insensitivity of the strain is related to the special domain structure of the rich BMT, which leads to a large gap between the ferroelectric relaxation transition temperature and the freezing temperature of the system, so it can be obtained in the wider range of temperature range and in the different states and states. In addition, the phase structure under different electric fields has an obvious influence on the stability of the temperature change and the different strain formation mechanism corresponding to the temperature stability. At the same time, this special domain structure can also make the system coexist with each state of the relaxation phase in the wider range of composition, and the composition of the system can be obtained. Sensitive large strain. This study provides a new design idea for the improvement of the strain performance of the bismuth perovskite system. See Chapter fourth. (4) using PMN to replace BiFe03 for the first time in the BiFe03-PbTi03-xPMN (BF-PT-xPMN) system, a low electric field is induced to produce a large electroinduced strain and a significant increase in the dynamic d33* of this kind of material. The composition of x=0.35 should be changed to 0.22-0.55% in the 2.5-7 kV/mm electric field interval, and the maximum dynamic d33'= ~ 1100 pm/V is obtained under the 3.5 kV/mm electric field. It is of great value for the practical application of the material. At the same time, the large strain with a smaller strain lag is obtained on the rich PMN side: the strain obtained by the x=0.68 composition in the 5 kV/mm electric field. For 0.33%, the strain lag is to 25%. through the study of the phase structure change of the different composition in the process of the electric field. It is found that the generation of large strain in the system is related to the relaxation ferroelectric transition (the growth of the polar nanoscale micro area) induced by the electric field, the reversal of the rhombus phase domain and the rhombus tetragonal phase transition. The additional contribution of strain generation plays an important role in improving the strain performance of the system. See fifth chapters. (5) through systematic analysis of the relationship between the electrostrain and structure of different bismuth perovskite systems, the mechanism of producing large strain and improving the strain performance of bismuth based perovskite system are further studied. First, we For the first time, it is clear that the essence of the relaxation ferroelectric reversible transformation process induced by the electric field is the growth of polar nanometers in the material under the action of the electric field, and the subsequent electric domain inversion and ferroelectric phase transition, and the evolution process of the domain of the bismuth perovskite system under the action of the electric field. Secondly, we reveal the phase in the process of the elevating electric field. The asymmetry of the changing process is the main cause of the strain lag in the relaxation ferroelectric system of the bismuth based perovskite, and then the purpose of reducing the strain lag is achieved through the composition optimization design. Through the analysis of the microstructure, we think that the asymmetric phenomenon of the phase transition process and the chemical ordered area are in the electric field during the period of the loading of the electric field. The motion and the enrichment at the domain walls of ferroelectric domains are described in the sixth chapter.
【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ174.1
【参考文献】
相关期刊论文 前1条
1 姚喜,陈至立;弛豫型铁电体[J];压电与声光;1984年06期
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