基于弛豫铁电单晶的1-1-3型压电复合元件研究

Piezoelectric composite is a key technology of modern underwater acoustics detection and ultrasonic testing. The bottleneck of conventional piezoelectric composite such as 0-3, 2-2, 1-3 type PZT/polymer composite has became more and more obvious for its limits on improving electeromechanical coupling coefficients and piezoelectric constants. In order to solve the above problems，relaxor ferroelectric single crystal with high piezoelectricity has been induced into 1-3 type composite. The electeromechanical coupling coefficient of 1-3 PMNT/polymer composite is up to 0.85. How to improve the electeromechanical coupling coefficient is one of the issues more concerned by researchers. In this research, an noval 1-1-3 type composite is proposed to increase the electeromechanical coupling coefficient. Relaxor ferroelectric single crystal is cutting into columns and surrounded by soft polymer. The other kind of hard polymer is manufactured to form a 3D grid structure. The relaxor ferroelectric single crystal and soft polymer are located in lattice of the hard polymer. The single crystal and soft polymer are connected itself in one dimensional and the hard polymer is connected itself in three dimensional. So this kind of composite is called 1-1-3 type composite.This kind of composite combines the advantages of high electeromechanical coupling coefficients, high piezoelectric constant, low cross coupling effect, broadband, high temperature stability and high mechanical stability.

压电复合元件是现代水声探测、超声检测中的关键元件，在军用及民用领域有较强的应用前景。以压电陶瓷为主动性材料，以0-3型、2-2型、1-3型结构构成压电复合材料在进一步提升机电耦合系数、提高压电性等方面遇到了瓶颈。为解决上述难题，研究者们将具有高压电性的弛豫铁电单晶引入压电复合材料中，制备了1-3型复合元件，此种结构复合元件的机电耦合系数已经可达到0.85，如何进一步提高复合元件机电耦合系数是研究者们近来较为关注的问题之一。本项目拟创造性的采用1-1-3型结构构成复合元件，以弛豫铁电单晶作为主动性材料，以柔性聚合物包裹单晶细柱，以刚性聚合物构成三维网格结构起到支撑作用。通过上述结构，使得该复合元件即保持单晶的强压电性能，又减小了基元间的横向耦合，同时还可以降低声阻抗，使其同时具有高机电耦合系数、阵元间振动耦合小以及机械和温度稳定性高的优点。

压电复合元件是现代水声探测、超声检测中的关键元件，在军用及民用领域有较强的应用前景。以压电陶瓷为主动性材料，以0-3型、2-2型、1-3型结构构成的压电复合材料在进一步提升机电耦合系数、提高压电性等方面遇到了瓶颈。为解决上述难题，本项目创造性的采用1-1-3型结构构成压电复合材料，以弛豫铁电单晶或压电陶瓷作为主动性材料，以柔性聚合物包裹压电细柱，以刚性聚合物构成网格结构起到支撑作用。通过上述结构，使得该复合材料即保持压电材料的强压电性能，又减小了基元间的横向耦合，同时还可以降低声阻抗，使其同时具有高机电耦合系数、低声阻抗、阵元间振动耦合小以及机械和温度稳定性高的优点。本文应用等效参数理论建立了1-1-3型压电复合材料的等效参数模型，求出了复合材料压电、介电等材料参数随各相材料参数及体积百分比变化关系。本文分别制备了基于压电陶瓷和基于弛豫铁电单晶（PMN-PT）的1-1-3型压电复合材料样品，并通过实验测量其性能，测量结果与理论计算结果吻合较好。其中基于压电陶瓷的1-1-3型压电复合材料，机电耦合系数达到0.69，声阻抗降低到6.82MRayl。基于弛豫铁电单晶的1-1-3型压电复合材料，机电耦合系数达到0.925，声阻抗降低到9.77MRayl。

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