【作者】 吕巍；

【导师】 张汉壮；

【作者基本信息】 吉林大学 ， 光学， 2008， 硕士

【摘要】 铌酸锂晶体和周期性极化铌酸锂晶体(PPLN)在传导器、探测器、光集成电路和声表面波等方面有着很广泛的应用前景,对它们的研究有着很重要的理论意义和应用价值。目前国内的研究主要集中在晶体制备以及器件研制方面。对于周期性极化铌酸锂晶体的本身性质,以及微观物理机制和规律方面缺少相关讨论。在本文中介绍了压电晶体以及铌酸锂晶体的发展和研究历史;对压电学的基本原理,以及压电方程的四种形式和四类边界条件作了介绍;归纳了铌酸锂和周期性极化铌酸锂晶体的基本物理特性、制备方法和相关参数的测量方法。主要讨论了周期性极化铌酸锂晶体的介电常数随外加微波源频率变化的关系,推导出介电常数随频率变化关系的公式,并且进一步讨论了在不同情况下,周期性极化铌酸锂晶体中介电常数随外加微波源频率变化的一般规律,并利用理论与实验结果的拟合确定了PPLN晶体的相关物理参数。本文的主要意义是通过对铌酸锂晶体的一些物理特性的讨论,总结出解决周期性极化铌酸锂晶体中介电常数随外加微波源频率变化的一般方法,讨论不同情况下的变化规律,提出了利用理论拟合实验结果确定物理参数的方法,为以后的理论研究做理论基础,为相关器件的研究提供理论依据。更多还原

【Abstract】 LiNbO3 (LN) is one of the most important piezoelectricity crystalloids . It has been researched by many people and used in many fields . It has very good physical and chemistry characters and it is easy to be made . So it is the emphasis in application and theory field of the piezoelectricity crystalloids .By the development of research and technique , people find a new field of the LiNbO3 that is called Periodically Poled LiNbO3 (PPLN) . Now , OPO , LIC , light-switch and so on are the most hot research fields of LN and PPLN .The piezoelectricity is the basic theory and tool to research the piezoelectricity crystalloids . For us , we must master the piezoelectricity equation . In second part of the dissertation , we conclude the piezoelectricity equation from the thermodynamics . Because of four forms of the boundary condition , the piezoelectricity equation also has four forms . In the third part of the dissertation , we discuss the crystal structure of LN . It is achromaticity or light yellow . It has the crystal structure as the same form as ABO3 ilmenite crystal . Its courier temperature is 1210℃.The facture of LN is still the hot field , especially PPLN . Although there are a lot of factures of LN and PPLN , people is still finding the better factures as the disadvantage of every found factures . Now , the most used facture of PPLN is called the outfield polarization .The elastic , piezoelectric and dielectric coefficients are the important physics coefficients of piezoelectricity crystalloids . For these physics coefficients , the method of measure is also mentioned in the third part of the dissertation .The relationship between dielectric coefficient and capacitance , impedance , energy wastage of piezoelectricity crystalloids is very compact , so it is important to research the dielectric coefficient . My main aim is that we can obtain the relationship between the dielectric coefficient of PPLN and the frequency of the microwave outfield when the frequency of the microwave outfield changed .We found two theory models to figure out the relationship between the dielectric coefficient of PPLN and the frequency of the microwave outfield .The theory models is based on these there assumptions .1. On the assumption that PPLN is absolutely pure .2. We assume that when the microwave transform though PPLN , the change of the temperature of environment and itself is tiny .3. We consider the all ferroelectric particles of PPLN as one particle . We use the fourth piezoelectricity equation and the Newton`s equation of motion to figure out the resonance frequency of model 1 .And n=1,2,3,…,N N is the number of periodicallyFor model 2 , we can use the same method to figure out the problem . It must be noted that we need to figure out the frequency for quasilongitudinal and quasishear wave in this model , respectively .For quasilongitudinal wave :For quasishear wave :Then we use Damp equation of motion to figure out the the relationship between the dielectric coefficient of PPLN and the frequency of the microwave outfield . In this situation dielectric coefficient is pluralism .For model 1For model 2 :We figure out the theory curve and make some conclusion by discussing the curve .For model 1 :1 . Same thickness of periods , different number of periods. The real part of the dielectric coefficient, with the increase in numbers, ferroelectric domains in the resonance frequency, but the inherent resonant frequency corresponding position remained unchanged; dielectric constant is the size of the different cycles of the crystal, corresponding resonance frequency is basically the same; for a crystal, with the resonance frequency to high frequency, amplitude and resonance of the dielectric constant is the size of it decreases, that is to say dispersion phenomenon weakened.For the imaginary part of permittivity, with the increase in thickness, the crystals in different number, in the corresponding resonance frequency basically the same, that is, the size of the basic relaxation energy equivalent to a crystal, with the resonance frequency to high Frequency development, the size of the imaginary part of permittivity decreases gradually, that is, to reduce energy relaxation .2 . Same number of periods , different thickness of periods.The real part of the dielectric constant, with the increase of thickness cycle, the initial and the corresponding resonance frequency direction to the low-frequency side, the corresponding size of the dielectric constant is change, which increased dispersion phenomenon. For a crystal, with the frequency increasing, the size of the dielectric constant is smaller dispersion phenomenon is weakening.For the imaginary part of permittivity, with the increase of thickness cycle, and the corresponding initial imaginary part of the dielectric constant of the peak close to the low-frequency, and the corresponding size of the imaginary part of the dielectric constant change, a change that energy relaxation . For a crystal, with the frequency increasing, the size of the imaginary part of permittivity smaller, smaller energy relaxation. For model 2 :1 . Same thickness of periods , different number of periods.The real part of the dielectric constant, with the number of cycles increasing resonance increase in the number of sports, but the initial and the corresponding resonance frequency did not change, the corresponding size of the dielectric constant is also no change to a crystal, as The increase in frequency from prospective longitudinal wave and quasi-transverse wave were real contribution to the dielectric constant is gradually smaller, but due to vibration superposition, in some locations, the size of the dielectric constant is there will be an increase.For the imaginary part of permittivity, with the increase in cycle, the number of crystals in different cycles, in the corresponding resonance frequency basically the same, that is, the relaxation of energy is basically the same size; With the increase in frequency, mode of different dielectric constant imaginary part is gradually getting smaller, that is, relaxation of energy is gradually getting smaller.2 . Same number of periods , different thickness of periods. The real part of the dielectric constant, with the increase of thickness cycle, the initial and the corresponding resonance frequency direction to the low-frequency side, the corresponding size of the dielectric constant is change, which increased dispersion phenomenon. For a crystal, with increasing frequency, from prospective longitudinal wave and quasi-transverse wave were real contribution to the dielectric constant of the size became smaller. However, due to vibration superposition, in some locations, the size of the dielectric constant is there will be an increase.For the imaginary part of permittivity, with the increase of thickness cycle, and the corresponding initial imaginary part of the dielectric constant of the peak close to the low-frequency, and the corresponding size of the imaginary part of the dielectric constant change, a change that energy relaxation . For a crystal, with increasing frequency, from prospective longitudinal wave and quasi-transverse wave imaginary parts, respectively contributions to the dielectric constant of the smaller size, or smaller energy relaxation.These theoretical results obtained, on the other theory can be played on the basis of theory, the practical application of a theoretical guiding role.更多还原