Rutkowski Paweł, Huebner Jan, Graboś Adrian, Kata Dariusz, Sapiński Bogdan, Faryna Marek
Department of Ceramics and Refractories, Faculty of Materials Science and Ceramics, AGH University of Science and Technology in Krakow, al. Mickiewicza 30, 30-059 Kraków, Poland.
Department of Process Control, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
Materials (Basel). 2020 Dec 16;13(24):5741. doi: 10.3390/ma13245741.
Analysis of dense Potassium Sodium Niobate (KNN) ceramic obtained by hot pressing (HP) method at 1100 °C are presented in this paper. The synthesis of KNN-based piezoelectrics meets the following challenges-low density of material, uncontrolled K/Na ratio, multiphase composition and formation of different KNN structures. The classical hot pressing approach results in contamination by carbon originating from graphite molds. The proposed hexagonal Boron Carbide (h-BN) layer between green sample and graphite mold could protect samples from carbon contamination. Additionally, the presence of h-BN may decrease the formation of oxygen vacancies, which allows us to maintain the semiconductor features of the KNN structure. Remaining issues were addressed with the addition of excess Na and ErO doping. The results showed that excess Na addition allowed us to compensate evaporation of sodium during the synthesis and sintering. ErO was added as sintering aid to limit abnormal grain growth caused by h-BN addition. The modification of amount of Na and ErO addition resulted in high purity KNN samples with tetragonal structure and apparent density higher than 97%. Finally, piezoelectric features of prepared dense samples were measured and presented.
本文介绍了通过在1100℃下热压（HP）法获得的致密铌酸钾钠（KNN）陶瓷的分析结果。基于KNN的压电材料的合成面临以下挑战——材料密度低、K/Na比不受控制、多相组成以及不同KNN结构的形成。传统的热压方法会导致来自石墨模具的碳污染。在生坯样品和石墨模具之间提议的六方碳化硼（h-BN）层可以保护样品免受碳污染。此外，h-BN的存在可能会减少氧空位的形成，这使我们能够保持KNN结构的半导体特性。通过添加过量的Na和ErO掺杂解决了其余问题。结果表明，添加过量的Na可以补偿合成和烧结过程中钠的蒸发。添加ErO作为烧结助剂以限制由添加h-BN引起的异常晶粒生长。改变Na和ErO的添加量得到了具有四方结构且表观密度密度高于97%的高纯度KNN样品。最后，对制备的致密样品的压电特性进行了测量并展示。
