超高介电常数氧氮化物ATaO2+xN1-x(A=Sr, Ba)的制备、微结构及其介电性能研究

The rapid development of electronic ceramic industry requires the use of ceramic capacitors with a high capacity. Compared with the most extensively applied BaTiO3 dielectrics, ATa(O, N)3 (A=Sr, Ba) oxynitrides have better dielectric properties and corrosion resistance. Their super-high dielectric constant is closely associated with their microstructures, which can be critically tuned by the processing approach (mainly involving synthesis and sintering). The common-occurring ammonolysis plus pressureless sintering route always consumes very long time and favors the decomposition of the oxynitrides during sintering, resulting in a low purity and relative density of the products. Thus, it is difficult to prepare oxynitrides with excellent properties by conventional methods..In this proposal, we focus on the processing of ATa(O, N)3 (A=Sr, Ba) oxynitrides to achieve the optimization of their dielectric properties. Urea route, a one-step method, is employed to fabricate ATaO2+xN1-x (A=Sr, Ba) powders with an O/N non-stoichiometry; and then, a two-step sintering approach, i.e., spark plasma sintering plus pressureless sintering, is used for rapid densification. The microstructure of the oxynitrides will be tuned for the optimization of the dielectric constant. The ceramic dielectrics with a good purity, a high density and superior dielectric properties are expected.

电子陶瓷工业的快速发展对大容量陶瓷电容器需求迫切。相对于广泛应用的BaTiO3介电陶瓷，ATa(O, N)3 (A=Sr, Ba)氧氮化物有着更好的介电性能及耐化学腐蚀性。其超高介电常数的获得与微结构密切相关，而制备工艺（主要包括合成和烧结）则是微结构调控的关键。目前主流的氨化合成加无压烧结的制备工艺时间过长，烧结过程中常发生氧氮化物分解，产物纯度和致密度偏低，因而较难获得综合性能优异的介电材料。. 本申请拟从制备工艺的角度对ATa(O, N)3 (A=Sr, Ba)氧氮化物的介电性能进行优化，采用尿素法一步合成具有非O/N化学计量比的陶瓷粉体ATaO2+xN1-x (A=Sr, Ba)，并利用放电等离子烧结加无压烧结的两步烧结法实现材料的快速致密化，优化其微结构，实现材料介电常数的可调性，以期制备出纯度好、密度高、介电性能优的介电陶瓷。

钙钛矿氧氮化物功能材料是近年来国际上研究的热点之一。本研究基于大容量介电陶瓷的应用需求及ATa(O, N)3 (A=Sr, Ba)氧氮化物优异的介电性能，针对目前主流的氨化加无压烧结的制备方法工艺时间长、产物纯度和致密度偏低等不足，在热力学计算的基础上，采用尿素法一步合成了高纯SrTa(O, N)3和BaTa(O, N)3陶瓷粉体，研究并掌握了尿素含量、升温速率、制备温度和保温时间等工艺条件对产物结构、组成及微观形貌的影响规律；在烧结热力学与动力学研究的基础上，采用放电等离子烧结结合氨化烧结的两步烧结工艺制备出了氧氮化物陶瓷块体；通过研究探明了材料微结构对其介电性能的影响机制，实现了对材料介电性能的调控，并最终得到了高纯度、高致密和高介电的氧氮化物陶瓷。其中，利用无压放电等离子煅烧技术不到10分钟即可完成粉体制备，较目前主流工艺耗时缩短99%；所制备的氧氮化物陶瓷纯度达~98%，致密度达~95%；在空气中耐温可达~600℃；在pH=1、pH=10和80℃热水中可稳定存在，无明显结构、组成和外观变化；在100Hz频率下介电常数高达12269（200℃），介电损耗低至0.001（室温）。本项目所取得的研究成果创新了钙钛矿氧氮化物的低成本快速制备工艺，其性能也是目前公开报道里最优之一，在高性能陶瓷电容器等领域有着广阔的应用前景。