Serrazina Ricardo, Ribeiro Camila, Costa Maria Elisabete, Pereira Luis, Vilarinho Paula M, Senos Ana M O R
Department of Materials and Ceramic Engineering, Campus Santiago, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal.
CENIMAT-I3N, Campus da Caparica, School of Science and Technology, FCT-NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
Materials (Basel). 2021 Mar 9;14(5):1321. doi: 10.3390/ma14051321.
The considerable decrease in temperature and time makes FLASH sintering a more sustainable alternative for materials processing. FLASH also becomes relevant if volatile elements are part of the material to be processed, as in alkali-based piezoelectrics like the promising lead-free KNaNbO (KNN). Due to the volatile nature of K and Na, KNN is difficult to process by conventional sintering. Although some studies have been undertaken, much remains to be understood to properly engineer the FLASH sintering process of KNN. In this work, the effect of FLASH temperature, T, is studied as a function of the particle size and impurity content of KNN powders. Differences are demonstrated: while the particle size and impurity degree markedly influence T, they do not significantly affect the densification and grain growth processes. The conductivity of KNN FLASH-sintered ceramics and KNN single crystals (SCs) is compared to elucidate the role of particles' surface conduction. When particles' surfaces are not present, as in the case of SCs, the FLASH process requires higher temperatures and conductivity values. These results have implications in understanding FLASH sintering towards a more sustainable processing of lead-free piezoelectrics.
温度和时间的大幅降低使快速烧结成为材料加工更具可持续性的替代方法。如果挥发性元素是待加工材料的一部分，例如在有前景的无铅碱基金属氧化物压电材料铌酸钾钠（KNN）中，快速烧结也变得很重要。由于钾和钠的挥发性，KNN很难通过传统烧结工艺进行加工。尽管已经开展了一些研究，但要恰当地设计KNN的快速烧结工艺，仍有许多有待了解的地方。在这项工作中，研究了快速烧结温度T作为KNN粉末粒径和杂质含量的函数的影响。结果表明存在差异：虽然粒径和杂质程度对T有显著影响，但它们对致密化和晶粒生长过程没有显著影响。比较了快速烧结的KNN陶瓷和KNN单晶（SCs）的电导率，以阐明颗粒表面传导的作用。当不存在颗粒表面时，如在SCs的情况下，快速烧结过程需要更高的温度和电导率值。这些结果对于理解快速烧结以实现无铅压电材料更可持续的加工具有重要意义。
