面对当前社会在医疗器械、军事通信等领域对材料的多元化、复杂化要求，压电材料多态化，结构功能一体化与高性能成为当前发展热点。通过在压电陶瓷中引入多孔结构可有效降低其声阻抗和密度，使其声阻抗与生物组织相匹配，提高其灵敏度，拓展了功能压电陶瓷作为声学换能器件的应用领域。本文以钛酸铋钠基压电陶瓷为研究对象，采用造孔剂法和冷冻干燥法制备具有多孔态的压电材料，系统分析其结构与性能特点，探索多孔结构与电学性能作用规律。

优选生物质核桃壳粉、淀粉和PMMA为造孔剂，制备了具有柱状、椭球状和球状孔结构的0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃(BNT-BT)陶瓷，相较于淀粉和PMMA构筑的椭球形与球形孔，核桃壳粉所构筑的多孔结构呈定向排列，孔径为1.5~4 μm，气孔率为7～20%，其压电常数d₃₃达到101 pC/N。介电常数在2600-4000范围内可调。基于有限元理论，探索分析了BNT-BT陶瓷中柱状、椭球状和球状孔对电场分布作用规律，表明定向排列一维多孔结构可有效提升压电陶瓷介电可调性，且不会导致介电损耗增加。有序孔隙之间的陶瓷层对孔隙结构附近的微应力和应变提供了有效的屏障，使多孔陶瓷压电性能稳定。

基于冷冻干燥法开发了具有高孔隙率的BNT-BT多孔陶瓷，多孔结构呈蜂窝状，平均孔径分布在120 μm到280 μm，多孔结构有序排列。当造孔剂含量相同，烧结温度为1125 ℃时制备的BNT-BT多孔陶瓷孔隙率为73%，介电常数为971。当孔隙率为68%时，压电常数为77 pC/N，声阻抗值最小为Z=2.63 Mrayls。分析发现有序排列的蜂窝多孔结构可保持较好的压电常数，有利于降低声阻抗，提高BNT-BT多孔陶瓷的静水压品质因数，有效提升了陶瓷与水生组织匹配的灵敏度。

在核桃壳粉制备的多孔BNT-BT陶瓷基础上，引入SrTiO₃对BNT-BT进行掺杂，以提高无铅压电陶瓷介电与压电性能。制备了(1-x)(0.94(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃)-xSrTiO₃ ((1-x)(BNT-BT)-xST)陶瓷，研究发现ST掺杂使多孔陶瓷矫顽场从20.66 kV/cm降低至11.67 kV/cm，压电常数最高为120 pC/N。利用多孔(1-x)(BNT-BT)-xST压电陶瓷设计薄圆片振子，进行模态分析，谐振峰明显对其径向伸缩模进行谐响应特性分析。当x=0.08时，陶瓷表现出良好的性能：k_p=0.1611、=0.3889、S11E =14.2272×10^-12 N/m²、k₃₁=0.0892、-d₃₁=34.65。具有定向排列多孔结构的陶瓷显示出较高的压电常数，本论文研究为其在电声换能领域的应用供技术支持。

As a result of the diversified and complex material requirements of the present society in medical devices, military communications, and other fields. The development of polymorphic and high performance piezoelectric materials has become one of the hottest areas of research in recent years. By introducing porous structures into piezoelectric ceramics, acoustic impedance and density can be effectively reduced. This results in an acoustic impedance that matches biological tissue. It also improves sensitivity, expanding applications for functional piezoelectric ceramics as acoustic transducer devices. Bismuth titanate sodium-based piezoelectric ceramics were used as the research subject in this study. The porous piezoelectric materials were prepared by using pore-forming agents and freeze-drying methods, and their structural and performance characteristics were systematically analyzed, and a law regarding porous structure and electrical performance was explored.

0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃(BNT-BT) ceramics with cylindrical, ellipsoidal and spherical pore structures were prepared by using biomass walnut shell powder, starch and PMMA as pore forming agents. Compared with the ellipsoidal and spherical pores constructed by starch and PMMA, the porous structures constructed by walnut shell powder were oriented, with pore sizes ranging from 1.5 to 4 μm and porosity ranging from 7 to 20%. The piezoelectric constant d₃₃ reaches 101 pC/N. Dielectric constant is adjustable in the range of 2911-3715. Based on the finite element theory, the effect of cylindrical, elliptic and spherical holes on electric field distribution in BNT-BT ceramics is explored and analyzed. Directional one-dimensional porous structures have been shown to enhance the dielectric tunability of piezoelectric ceramics without increasing dielectric loss. The ceramic layers between the ordered pores provide an effective barrier to microstresses and strains in the vicinity of the pore structure, resulting in stable piezoelectric properties of the porous ceramics.

BNT-BT porous ceramics with high porosity were prepared by freeze-drying methods. There was an orderly arrangement of the honeycomb porous structure with average pores ranging from 120 to 280 μm. When the content of pore-forming agent is the same and the sintering temperature is 1125 ℃, the porosity of BNT-BT porous ceramics is 73% and the dielectric constant is 971. When the porosity is 68%, the piezoelectric constant is 77 pC/N and the minimum acoustic impedance is Z=2.63 Mrayls. It is shown that the porous structure of the ordered honeycomb is capable of maintaining good piezoelectric properties, reducing acoustic impedance, improving the hydrostatic quality factor of BNT-BT porous ceramics, as well as improving the sensitivity of the ceramic to aquatic tissues.

In order to improve the dielectric and piezoelectric properties of lead-free piezoelectric ceramics, SrTiO₃ was introduced into porous BNT-BT ceramics prepared from walnut shell powder. (1-x)(0.94(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃)-xSrTiO₃((1-x)(BNT-BT)-xST) ceramics were prepared by solid phase method. By adding ST doping to porous ceramics, the coercive field was reduced from 20.66 kV/cm to 11.67 kV/cm with piezoelectric constants of up to 120 pC/N. The porous (1-x)(BNT-BT)-xST piezoelectric ceramics were used to design thin plate vibrators, and the modal analysis was carried out. When x=0.08, ceramics show good performance: k_p=0.1611、=0.3889、S11E =14.2272×10^-12 N/m²、k₃₁=0.0892、-d₃₁=34.65. Ceramics with orientationally aligned porous structures show high piezoelectric constants. This study provides technical support for their applications in areas such as hydroacoustic transducer and electroacoustic transducer.