KTN晶体极性纳米微区的诱导演化、动态电光响应及其性能调控研究

It is of great importance to explore the mechanism of the large electro-optic response of crystals. KTN crystals have attracted great attention from scientists because of the giant quadratic electro-optic effect near paraelectric-ferroelectric phase boundary. Besides, the establishment of polar nanoregions (PNRs) in KTN can eliminate the light scattering of domain near the phase boundary, and realize scale free optics. The relationship between the PNRs and enhancement of the macroscopic optical properties near the phase boundary has not been fully understood. Choosing PNRs in KTN as the research object, the induced evolution, dynamic electro-optic response, and regulation of PNRs would be investigated against two key scientific questions, which are assigned to "Induced evolution mechanism and regulation of PNRs" and "Correlation of the structure of PNRs in microscopic to the enhanced electro optical properties of KTN in macroscopic". Combined with first principles calculations, this project will reveal the evolution mechanism of PNRs under the inducing conditions, establish relationship among the PNRs structure, dynamic electro-optic response, and macroscopic electro-optic performance, clarify the physical mechanism of electro-optic performance enhancement of KTN crystal. This project is of great scientific importance and practical value in discovering the basic relationship between macroscopic property and microscopic structure of solid solution crystal with perovskite structure, laying theoretical and experimental foundation for the regulation of PNRs, and promoting the practical application of KTN crystals.

探索固溶体大电光效应的起源是当前的研究热点和前沿。相界附近钽铌酸钾晶体（KTN）具有巨电光效应，调控其内部极性纳米微区（PNRs）的结构，可消除畴对光的散射，实现光的无尺度传输。PNRs增强KTN光学性能的机理尚不清楚。项目拟以KTN晶体相界附近的PNRs为研究对象，针对“PNRs的诱导演化机制”和“PNRs的结构与KTN宏观电光性能增强的内在关联”两个关键科学问题，提出通过调控局域结构和构建局域空间电荷场诱导PNRs的演化，开展PNRs的动态电光响应特性及其性能调控研究。结合第一性原理计算，揭示局域结构和光致空间电荷场诱导下PNRs的演化规律和机制，建立PNRs结构-动态电光响应-宏观电光性能之间的关系，阐明KTN晶体电光性能增强的物理机理。项目有助于探索钙钛矿结构固溶功能晶体的结构-性能关系，为PNRs的调控奠定理论和实验基础，对推动KTN晶体的实用化具有重要科学意义和应用价值。

固溶体单晶的光电特性与微观结构之间构效关系的构建是光电领域进一步发展的关键，同时其物理机制的明确也是该领域亟待解决的问题之一，一直以来受到了广泛的关注。本项目基于“PNRs的诱导演化机制”和“PNRs的结构与KTN宏观电光性能增强的内在关联”两个关键科学问题，分别探究了温度场、电场、空间电荷场以及组分梯度场等对KTN晶体电光特性的调控。结合电光特性的响应特征，通过PFM、拉曼光谱以及TEM等手段对PNRs在外场作用下的动态特性以及结构的诱导演变进行表征，建立外场、PNRs动态特征以及宏观电光特性之间的对应关系，并在此基础上实现了电光系数的显著增强，为进一步利用外场改良KTN系列晶体光电特性提供了依据。通过物理模型的构建以及模拟计算，明确了KTN晶体内部微观畴(PNRs)结构与宏观性能之前的构效关系，阐明了PNRs以及电光特性对外场的响应机制，为探索优异的电光材料奠定了基础。