以铋层状结构材料为代表的单相多铁性材料，由于其在室温以上同时具有铁磁性和铁电性，使其在存储器等领域中有重要的潜在应用。掺杂、共生等材料功能化改性的方法能够大幅提高多铁性材料的铁电、铁磁性能，但也会明显改变多铁性材料的微观结构。大量实验和理论分析证明，铋层状结构材料的晶体结构稳定性和宏观铁电性能具有明显的结构依赖特性。为了揭示和分析铋层状结构材料铁电等宏观性能的结构依赖的微观原因，必须确定和描述对层状多铁性材料宏观性质有重要影响的微观缺陷态的动静态特性。本项目预期利用最新的核探测器和读出电子学方法研制基于SiPM的32路全数字化便携式正电子湮没寿命谱仪，并结合其它表征手段，测量分析铋层状结构材料中相关缺陷态的分布和变化规律，获取铋层状结构材料中缺陷的演变机理，为铋层状材料功能化设计过程中微观结构的控制和形貌的优化提供有力的理论依据。

Bismuth layer-structured ferroelectrics have drawn the most attention due to potential applications in ferroelectric random access memories. The dielectric and piezoelectric properties in ferroelectrics is largely enhance due to the doping and intergrowth effects. Studies show strong dependence of structural and ferroelectric properties on the crystal structure and orientation. Defect morphology and the relationship of its static and dynamic mechanisms are need in order to reveal the unique structural dependence properties. This project will use the up-to-date techniques of nuclear electronics and detection to build a compact digital positron annihilation lifetime spectroscopy with an array of 32 Silicon Photo-multipliers (SiPM). Positron annihilation techniques and other characterization methods are used for the identification and characterization the structure-dependent physical properties. This study will also make theoretical progress to understand the relationship between structural stability and ferroelectric properties in the bismuth layer-structured ferroelectrics.