From FAST to FLASH: Field assisted sintering of oxide ceramics with controlled electric field and current density

闪速烧结是一种新型的陶瓷材料致密化工艺。该工艺是基于通过施加电场和外部加热相结合来迫使陶瓷体内的电流流动。在与材料电阻率相关的起始温度下，样品变得具有足够的导电性，高电流开始通过样品，伴随着明亮的光发射和在几秒钟内非常快速的致密化。由于电功率几乎完全被样品耗散，因此讨论了闪烧是一种非常节能和经济的方法。到目前为止，闪速烧结仅在实验室规模上使用小狗骨或棒状样品进行了演示。大多数影响闪速烧结的因素在文献中都是在非常基础的水平上描述的，但是据我们所知，对闪速烧结和工艺参数如何相互作用的系统研究仍然缺乏。提出了一种通过可靠地避免热点形成、控制致密化和调整微观结构来稳定闪蒸事件的研究思路。实现这些目标的关键是发展电流速率或功率速率控制的闪速烧结模式，迄今为止在文献中很少有描述。基于数值模拟计算温度分布将有力地支持实验工作。spp1959第一阶段通过演示钆掺杂铈的电流控制速闪烧结所取得的结果支持了这一概念成功的前景。在闪速烧结领域开始了与主要科学家的合作工作，这将在SPP 1959的第二阶段继续进行。此外，在spp1959第一阶段开发的预测致密化和晶粒生长的模型将被放大，包括闪速烧结的特定效应，如高电场的影响。

Flash sintering is a novel process for densification of ceramic materials. The process is based on forcing a current flow within a ceramic body by applying an electric field in combination with external heating. At an onset temperature, which is - amongst others - related to the material resistivity, the sample becomes sufficiently conductive and high electric current starts to pass through the sample accompanied by bright light emission and very fast densification in few seconds. Due to the fact that the electric power is almost completely dissipated by the sample, flash sintering is discussed to be very energy efficient and economic.Up to now, flash sintering has been only demonstrated on lab-scale using small dog-bone or bar shaped samples. Most influence factors of flash sintering are described on a very fundamental level in literature, but a systematic study how flash sintering and processing parameters interact is – to best of our knowledge – still lacking. A research concept is proposed, which aims on stabilizing the flash event by reliably avoiding hot spot formation, controlling the densification and tuning the microstructure. Main key for achieving these goals will be the development of current rate or power rate controlled flash sintering mode, which has been only rarely described in literature so far. Experimental work will be strongly supported by calculating the temperature distribution based on numerical simulations. Prospect of success of this concept is supported by results achieved during the first period of SPP 1959 by demonstrating current rate controlled flash sintering of Gadolinium doped ceria. Collaboration work with leading scientists in the field of flash sintering was initiated, which will be continued in the second period of SPP 1959. Furthermore, the model developed in the first period of SPP 1959 to predict densification and grain growth will be amplified by including specific effects of flash sintering, e.g. influence of high electric field.