Chemical stability of KNbO3, NaNbO3, and K0.5Na0.5NbO3 in aqueous medium
Chemical stability of KNbO3, NaNbO3, and K0.5Na0.5NbO3 in aqueous medium
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DOI：
10.1111/jace.15291
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发表时间：
2018-03
影响因子：
3.9
通讯作者：
O. Ozmen;C. Ozsoy-Keskinbora;E. Suvacı
中科院分区：
文献类型：
--
作者：
O. Ozmen;C. Ozsoy-Keskinbora;E. Suvacı
近年来，铌酸钾钠（K0.5Na0.5NbO3， KNN）在钙钛矿无铅压电陶瓷体系中得到了广泛的应用。在本研究中，研究了KNN粉末在水介质中的化学稳定性与pH、时间和粉末表面积的关系。为了更好地了解络合物KNN的溶解行为，首先分别研究了铌酸钾（KNbO3， KN）和铌酸钠（NaNbO3， NN）等亚组分。结果表明，该结构中的阳离子均发生不同值的溶解。表明KNN在水介质中发生不一致溶解，A位阳离子在较低pH下溶解较多，而B位阳离子在较高初始pH下溶解较多。释放的阳离子浓度（CA1 = K > CA2 = Na > CB = Nb）与阳离子场强度（FS）顺序呈反比关系，即在pH 4、7和10时，NN、KN和KNN的B = Nb5+FS > A2 = Na+FS>A1 = K+FS。根据ICP数据计算出的扩散层厚度在TEM图像中证实为外非晶层。此外，正规化阳离子浓度与粉末表面积的比值表明，扩散步骤驱动了不一致的溶解动力学。
In recent years, potassium sodium niobate (K0.5Na0.5NbO3, KNN) has become popular and promising among perovskite lead-free piezoceramic systems. In this study, the chemical stability of KNN powders in aqueous medium was investigated as a function of pH, time, and powder surface area. To better understand the dissolution behavior of the complex KNN stoichiometry, subconstituents such as potassium niobate (KNbO3, KN) and sodium niobate (NaNbO3, NN) were investigated separately first. Results showed that all of the cations in the structure underwent dissolution in different values. Indicating that KNN undergoes incongruent dissolution in aqueous medium, the dissolution of A site cations was higher at lower pH while the dissolution of B site cations increased at higher initial pH. The order of released cation concentrations (CA1 = K > CA2 = Na > CB = Nb) fits with inverse relationship of cation field strength (FS) order, B = Nb5+FS > A2 = Na+FS>A1 = K+FS, at pH 4, 7 and 10 for NN, KN, and KNN. Calculated diffuse layer thickness from the ICP data confirmed to outer amorphous layer in TEM image. Also, the ratio of normalized cation concentration versus surface area of powders showed that incongruent dissolution kinetic was driven by the diffusion step.