无铅铁电陶瓷的晶格振动及电子跃迁特性研究

发布时间：2019-06-09 23:00

【摘要】：无铅型铁电陶瓷材料由于其优良的铁电性能,对环境的友好性等,是当前铁电陶瓷材料的研究热点之一。目前,无铅型铁电材料的研究主要集中在：1)钙钛矿型钛酸盐系铁电材料,如钛酸钡BaTiO3(BT),钛酸锶SrTiO3(ST),钛酸锶钡(BaxSr1-x)TiO3(BST)等。2)钨青铜型的铌酸盐系铁电体,如铌酸锶钡SrxBa1-xNb2O6(SBN)等。3)含Aurivillius层状结构的铁电体。例如钛酸铋Bi4Ti3O12,铌酸锶铋SrBi2Nb209(SBNO)等。其中BST, SBN以及SBNO及其掺杂铁电材料具有较高电阻率、良好的抗疲劳特性、高介电常数等特点,在热释电探测器、紫外探测器、非制冷红外探测器、非制冷红外焦平面阵列和铁电存储等领域具有很大的应用前景。随着各行各业对高热释电、高介电可调性等性能材料的需求日益增加,无铅型铁电陶瓷的制备,性能及改性研究已成为铁电陶瓷材料的一个研究热点。根据目前科研工作者对铁电材料用于热释电探测器的工作原理的分析,热释电探测器的理想工作温度范围应在热释电材料的居里温度(Tc)点附近,这也就相应提高了探测器对环境温度的要求。所以降低这一类铁电材料的相变温度点是作为下一代热释电探测器开发的必要条件。因此,本论文采用光谱测量手段系统研究了无铅型铁电氧化物及其稀土元素掺杂的铁电材料如Ba0.4Sr0.6-xMnxTiO3(BSMT), SrxBa1-xNb2O6(SBN)和SrBi2Nb2-xNdxO9(SBNN)等陶瓷的合成、电子结构、光学声子振动模式及其居里温度特性的改善。本文的主要工作和创新点包括以下几点：一、研究了含铋层状结构铁电陶瓷SBNN在80-873K温度范围内的拉曼光谱,远红外光谱,以及椭圆偏振光谱。详细讨论钕元素Nd的掺杂对SBNN的电子结构,光学声子模式,以及居里温度的影响。对传统固态烧结反应制备的SrBi2Nb2-xNdxO9(0≤x≤0.20)研究表明,(a)通过对SBNN在80K的拉曼光谱分析得到,由Nb06氧八面体中产生的峰位在207cm-1的A1g[Nb]声子模式的频率随着Nd组分的增加而减少,随着温度的增加,A1g[Nb]声子模式的峰位及其强度在SBNN的铁电相到顺电相的相变温度附近都显示出不连续性。(b)通过Lorentz振子模型拟合SBNN在350-1500cm-1范围内的远红外反射光谱,我们发现5个红外活性的声子模式。由于Nd组分的增加导致的晶格畸变,Nb06倾斜和对称拉伸模式随着Nd组分的增加而减少。这和拉曼活性的声子振动模式的变化行为是一致的。通过拟合得到的高频介电常数在4.55到4.80之间,显示了Nd组分对远红外介电函数的影响。(c)通过在0°到500°变温椭圆偏振光谱,用Tauc-Lorentz色散模型拟合分析得到了SBNN的两个带间跃迁能量(在0°时跃迁能量分别为3.70和4.78eV)以及对应能量范围内的介电函数。在靠近铁电到顺电的相变温度时,这两个带间跃迁能量随着温度的升高都存在一个反常的变化。这种带间跃迁的变化是因为在晶格畸变过程中Bi6s和O2p轨道的杂化产生的。最后我们发现：在Bi202层中引入了Nd离子后,我们从Nb-O1-Nb的键角得到了Nb06氧八面体的倾斜角度,从9.7°减少到5.5°,进而减弱了Nb06氧八面体的扭曲程度,最后导致了的SBNN的居里温度随着Nd组分的增加,从710减少到550K。这对作为研究和开发下一代热释电红外探测器材料提供了科学依据。二、研究了钙钛矿型铁电陶瓷BSMT在紫外到远红外光子能量范围内的光学常数,禁带宽度等变化,并详细讨论Mn的掺杂对红外及拉曼声子模式,以及电子结构的影响。对传统固态烧结反应制备的Bao.4Sr0.6-xMnxTiO3(0.01≤x≤0.10)研究表明,(a) XRD分析结果表明,在1%至10%的Mn掺杂范围内,BSMT是单一的钙钛矿相,没有其他杂相的存在。(b)由于Ti06氧八面体随着Mn组分的增加而产生的畸变,拉曼活性的声子模式A1(LO3)/E(LO)的频率蓝移8cm-1。红外活性的T04声子模式的频率从532减少到520cm-1。(c)在1.0到3.0eV范围内,BSMT的介电函数ε2随Mn组分的增加而增加。光学禁带宽度(乓)在3.40到3.65eV之间,并且发现Eg随着Mn组分的增加而减少,需要指出的是在Mn则分增加到10%之后,ε2和Eg都有一个反常的变化。该研究为BSMT铁电陶瓷在新型光电多功能器件上的潜在应用提供了科学依据。三、研究了钨青铜型铁电陶瓷SBN的拉曼及红外活性的低频声子振动模式,得到其随着Sr组分以及温度的变化特性,观察到SBN的软模在相变点附近消失,由此得到SBN的居里温度随组分的变化关系。通过变温拉曼散射和傅里叶红外光谱技术探讨SrxBa1-xNb206(0.30≤x≤0.50)铁电陶瓷的异常晶格振动特性。(a)红外活性的的T2u。声子模式的频率随着Sr组分的增加,红移了大约2cm-1。原因是较大的Ba离子导致了铌八面体的变形。(b)从150到750K的变温拉曼光谱分析得到,随着温度的升高,Alg声子模式的频率向低频方向移动,强度明显降低,并且展宽明显变大。在居里温度点附近,A1g声子模式的频率和半高宽随温度变化的斜率均发生异常变化。SBN陶瓷的软模大约在42cm-1。随着温度的升高,软模的频率逐渐减少,耦合并最后消失。基于这些声子模式随温度的变化规律,我们得到SBN的居里温度与Sr组分之间的关系：Tc (x)=556-371x。
[Abstract]:The lead-free ferroelectric ceramic material is one of the hot spots of the present ferroelectric ceramic material due to its excellent ferroelectric property and the friendliness of the environment. At present, the research of lead-free ferroelectric materials is mainly focused on:1) Perovskite-type titanate-based ferroelectric materials, such as titanium, BaTiO3 (BT), SrTiO3 (ST) of titanium, Sr1-x (BST), and the like. Such as, for example, a lithium titanate Bi4Ti3O12, a ferroic acid, or a SrBi2Nb209 (SBNO), and the like. wherein the BST, the SBN and the SBNO and the doped ferroelectric material thereof have the characteristics of higher resistivity, good anti-fatigue property, high dielectric constant and the like, And has a great application prospect in the fields of non-refrigeration infrared focal plane arrays and ferroelectric storage. The preparation, performance and modification of lead-free ferroelectric ceramics have become a hot spot of the ferroelectric ceramic material. The ideal operating temperature range of the pyroelectric detector should be in the vicinity of the Curie temperature (Tc) of the pyroelectric material according to the analysis of the working principle of the ferroelectric material for the pyroelectric detector. Therefore, the phase-change temperature point of the ferroelectric material is reduced as a necessary condition for the development of the next generation pyroelectric detector. In this paper, the synthesis of lead-free ferroelectric oxide and its rare-earth element-doped ferroelectric materials, such as Ba0. 4Sr0.6-xMnxTiO3 (BSMT), SrxBa1-xNb2O6 (SBN) and SrBi2Nb2-xNdxO9 (SBN), are studied by means of spectral measurement. The main work and innovation points of this paper include the following: 1. Raman spectrum, far infrared spectrum and elliptically polarized light in the temperature range of 80-873 K of ferroelectric ceramic SBN with layered structure are studied. The electron structure, the optical phonon mode and the curie temperature of the doping of the element Nd in detail are discussed in detail. In response, the research on SrBi2Nb2-xNdxO9 (0-x-0.20) prepared by the conventional solid-state sintering reaction shows that (a) the frequency of the A1g[Nb] acoustic submode produced by the Nb06 oxygen octahedron is reduced with the increase of the Nd component as the temperature increases with the increase of the Nd component, In addition, the peak position of the A1g[Nb] acoustic submode and its intensity show no difference in the ferroelectric phase of the SBN to the phase transition temperature of the paramagnetic phase. and (b) fitting the far infrared reflection spectrum of the SBN in the range of 350-1500 cm-1 by a Lorentz oscillator model, Submode. The Nb06 tilt and symmetric draw mode as the Nd component increases due to the lattice distortion due to the increase in the Nd component and the change behavior of the phonon mode of the raman activity is The high-frequency dielectric constant obtained by fitting is between 4.55 and 4.80, and the far-infrared dielectric function of the Nd component is shown. (c) The two band transition energies of SBN (the transition energy of 3.70 and 4.78 eV at 0 掳 and 3.70 and 4.78 eV at 0 掳, respectively) and the corresponding energy range were obtained by using the Taurc-Lorenz dispersion model to obtain the elliptical polarization spectrum at the temperature of 0 掳 to 500 掳. An electrical function. When a phase change temperature near the ferroelectric to a paraelectric, there is an anomaly in the transition energy between the two bands as the temperature increases. The change of the band-to-band transition is due to the hybridization of the Bi6s and the O2p orbitals during the lattice distortion. Finally, we found that, after the introduction of Nd ions in the Bi202 layer, we obtained the inclination angle of the Nb06 oxygen octahedron from the bond angle of Nb-O1-Nb, and the degree of distortion of the Nb06 oxygen octahedron was reduced from 9.7 掳 to 5.5 掳, and finally the Curie temperature of the SBN was reduced with the Nd component. increases from 710 to 5 50 K. This provides a family for research and development of the next generation of pyroelectric infrared detector materials The optical constants and the forbidden band width of the perovskite type ferroelectric ceramic BSMT in the range of ultraviolet to far infrared photon energy are studied, and the doping of Mn to the infrared and Raman phonon modes and the electron are discussed in detail. The results of the study on the structure of Bao. 4Sr0.6-xMnxTiO3 (0.01% x {0.10) prepared by the traditional solid-state sintering reaction show that, in the range of 1% to 10% of the Mn doping range, the BSMT is a single perovskite phase and does not (b) the frequency of the acoustic submode A1 (LO3)/ E (LO) of the Raman activity due to the distortion of the Ti06 oxygen octahedron with the increase of the Mn component Blue shift of 8 cm-1. The frequency of the T04 acoustic submode of the infrared activity is reduced from 532 to 520 cm-1. (c) in the range of 1.0 to 3.0 eV, the dielectric function of BSMT is 2 with the Mn group. the increase in the fraction increases. the optical forbidden band width (e) is between 3.40 and 3.65 ev, and it is found that the eg decreases with the increase of the mn component, it is noted that after the mn is increased to 10%, both the bv2 and the eg are An abnormal change. The study is a potential application of the BSMT ferroelectric ceramics to a new type of photoelectric multi-function device The low-frequency phonon modes of the Raman and infrared activity of the tungsten-bronze ferroelectric ceramic SBN are studied in this paper. With the change of the Sr component and the temperature, the soft-mode of the SBN is observed to disappear in the vicinity of the phase-change point, and the Curie temperature of the SBN is obtained. The relationship of the degree with the composition is discussed. SrxBa1-xNb206 (0.30-x-0.50) ferroelectric is investigated by means of temperature-varying Raman scattering and Fourier infrared spectroscopy. The abnormal lattice vibration characteristics of the ceramic. a) the frequency of the infrared active T2u. The frequency of the phonon mode increases with the increase of the Sr component And the red shift is about 2 cm-1. The reason is that the larger Ba is off. and (b) the frequency of the Alg acoustic submode is shifted to the low frequency direction as the temperature is increased, and the intensity is obviously In the vicinity of the Curie temperature point, the frequency of the A1g acoustic submode and the half-height width change with the temperature There was an abnormal change in the slope of the chemical. The SBN ceramic The soft modulus is about 42 cm-1. With the increase of the temperature, the frequency of the soft die is The relationship between the Curie temperature and the Sr component of SBN is obtained based on the change of temperature.
【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM221

【相似文献】