Solid-State Reaction Mechanism and Deliquescence Phenomenon of KNaNbAlO Ceramic.

Development of (K,Na)NbO-based ceramics has attracted much attention in recent decades. In this work, KNaNbAlO ceramic was prepared using conventional solid-state processing. A deliquescence phenomenon was observed when the specimen was exposed to moist atmosphere. The reaction mechanism and cause of deliquescence were investigated using x-ray diffraction analysis, scanning electron microscopy, energy-dispersive spectrometry, electron microprobe analysis, inductively coupled plasma mass spectrometry, and thermogravimetric/differential scanning calorimetric analysis. The results revealed interactions mainly amongst the raw materials KCO, NaCO, and NbO as well as KCO, NaCO, and AlO, which can influence the sintering behavior of the mixture. (K,Na)NbO and (K,Na)AlO were present in the sintered KNaNbAlO ceramic, with the latter leading to deliquescence. During the sintering process, AlO reacts with alkali oxides (NaO and KO), which are the decomposition products of carbonates, to form (K,Na)AlO. In addition, AlO is more likely to react with KO compared with NaO. [ABSTRACT FROM AUTHOR]