Electrostriction in Ceramics and Glass

多年来，人们对包装材料的电学、机械和热性能进行了深入的研究，但关于低介电常数氧化物和氮化物的电致伸缩系数的可靠数据却很少。电致伸缩是力学应变与电场平方有关的第四阶张量性质。该项目的主要目标是对陶瓷和玻璃进行机电测量，这些无机材料是用于多层封装、金属硅器件、高压绝缘体、光纤、微机电机械系统和厚膜基板的代表性无机材料。要研究的材料包括二氧化硅、氮化硅、氧化铝、氮化铝、橄榄石、尖晶石、莫来石、堇青石、硅酸盐玻璃、云母和瓷器。PI和他的团队开发了两种测量陶瓷和玻璃电伸缩系数的技术。“直接”方法包括用仔细校准的光学干涉仪测量场致应变。“逆向”方法需要监测介电常数作为机械应力的函数。本项目的主要目的是建立描述电致伸缩系数与原子键类型、原子键长度、晶体结构和材料化学成分的依赖关系的结构-性能关系。由于电致伸缩是电极化和机械应变之间的主要耦合机制，因此PI希望确定电致伸缩系数、弹性柔度和介电常数之间的相关性。多年来，人们对包装材料的电学、机械和热性能进行了深入的研究，但关于低介电常数陶瓷和玻璃的电致伸缩系数的可靠数据却很少。提出的研究目标是测量各种陶瓷和玻璃材料的电致伸缩系数。电致伸缩是力学应变与电场平方有关的第四阶张量性质。它存在于所有绝缘体中，在用作电容器和换能器的铁电陶瓷中，以及在存在极高场的电子和光学器件中，它变得尤其重要。这包括光纤、高压绝缘体、激光窗、多层电子封装、薄膜元件和厚膜基板。在这些材料中，电场引起的应力和应变往往大得惊人，使得电致伸缩成为一种重要的降解机制。如果能找到零电致伸缩系数的材料，基于该材料的电子和光学器件的可靠性将大大提高。＊＊＊

9634101 Newnham The electrical, mechanical, and thermal properties of packaging materials have been investigated thoroughly over the years, but reliable data on the electrostriction coefficients of low-permittivity oxides and nitrides are scarce. Electrostriction is a fourth rank tensor property relating mechanical strain to the square of the electric field. The principal goal of this project is to carry out electromechanical measurements on ceramics and glasses representative of the inorganic materials used in multilayer packaging, metal-on-silicon devices, high voltage insulators, optical fibers, micro-electrical mechanical systems, and thick film substrates. Among the materials to be studied are silica, silicon nitride, alumina, aluminum nitride, forsterite, spinel, mullite, cordierite, silicate glasses, mica, and porcelain. The PI and his group have developed two techniques for measuring the electrostriction coefficients of ceramics and glasses. The 'direct' method involves measuring the field-induced strain with a carefully calibrated optical interferometer. The 'converse' method entails monitoring the dielectric constant as a function of mechanical stress. The principal purpose of this project is to formulate structure-property relationships describing the dependence of the electrostrictive coefficient on atomic bond type, atomic bond length, crystal structure, and chemical composition of the material. Since electrostriction is the primary coupling mechanism between electric polarization and mechanical strain, the PI hopes to identify correlations between electrostriction coefficients, elastic compliance, and dielectric permittivity. %%% The electrical, mechanical, and thermal properties of packaging materials have been investigated thoroughly over the years, but reliable data on the electrostriction coefficients of low-permittivity ceramics and glasses are scarce. The goal of the proposed research is to measure the electrostriction coefficient of a variety of ceramic and glass materials. Electrostriction is a fourth rank tensor property relating mechanical strain to the square of the electric field. It is present in all insulators and becomes especially important in the ferroelectric ceramics used as capacitors and transducers, and in electronic and optical devices where extremely high fields are present. This includes optical fibers, high voltage insulators, laser windows, multilayer electronic packages, thin film components and thick film substrates. In these materials the stresses and strains caused by electric fields are often surprisingly large, making electrostriction an important degradation mechanism. If materials having a zero electrostrictive coefficient could be found, the reliability of electronic and optical devices based on that material could be significantly improved. ***