冷烧并低氧分压退火KNN基压电陶瓷的制备及其结构与电学性能研究

常规空气烧结KNN基压电陶瓷面临烧结温度高、烧结窗口窄、使用贵金属电极等问题。低温制备KNN基陶瓷及多层陶瓷内电极贱金属化，对电子元件成本降低及节能生产意义重大。本研究拟发展全新冷烧技术，实现120~300摄氏度添加液相冷烧获得致密度高于90%的试样，继而在600~800摄氏度低氧分压退火得到致密度高于95%、电学性能良好的KNN基陶瓷。将致密KNN基陶瓷的制备温度从1000摄氏度以上降至K、Na元素挥发点以下，温区窗口从40摄氏度拓宽至200摄氏度，并实现贱金属电极使用。系统研究低温冷烧参量及中温低氧分压退火参量对陶瓷微观结构和电学性能的影响规律；探究冷烧传质机理；以参量对陶瓷阳离子挥发、晶体结构、畴结构和显微组织的影响为切入点，弄清冷烧陶瓷电学性能变化的结构根源。本研究为压电陶瓷的低温制备发展新途径，对解决元素挥发及贱金属电极使用等具有重要意义。

For sintering KNN -based ceramics in air via the conventional method, there exist some problems, including high sintering temperature, narrow temperature range for sintering, electrodes using precious metal, etc. Low-temperature synthesizing KNN -based ceramics and utilizing base metal as internal electrodes in multilayer ceramics play key role for decreasing cost and saving energy during production. In this project, we intend to study a new cold sintering method. With adding some given liquids into the ceramic precursor powders and being followed by cold sintering at temperatures between 120 celsius and 300 celsius, the samples with relative densities higher than 90% are expected to be obtained. The cold-sintered samples are then annealed at temperatures between 600 celsius and 800 celsius and in low oxygen partial pressure (pO2). Then, it is expected to obtain dense KNN -based ceramics with relative density higher than 95% and excellent electrical properties. By means of cold sintering, the temperatures for preparing KNN -based ceramics can be decreased from those higher than 1000 celsius to the volatilization points of K and Na elements. The temperature range for obtaining dense KNN -based ceramics can be remarkably widened from 40 celsius to 200 celsius. The base metal can be used as electrodes in devices. We intend to study variations in microstructure and electrical properties of the ceramics with the change of low-temperature cold sintering parameters and parameters of medium-temperature annealing in low pO2. Mass transfer mechanism during cold sintering will be explored. By exploring effects of synthesis parameters on volatilizationof cations, crystallite structure, domain structure and microstructure of the ceramics,the intrinsic relations between structure and electrical properties of the KNN-based ceramics will be obtained. The study provides a new way for low-temperature synthesizing piezoelectric ceramics. It is also very important for avoiding volatilization of the volatile elements in the ceramics and using base metal as electrodes.