熔盐法制备柱状铌酸钾钠粉体及其陶瓷

Preparation of Columnar Potassium-Sodium Niobate Powders and Ceramics by Molten Salt Synthesis

采用二步熔盐法合成了柱状铌酸钾钠粉体,并制备了致密的铌酸钾钠陶瓷。首先使用少量KSr2Nb5O15粉体作为晶种,以Nb2O5、KCl与不同SrCO3和Nb2O5的摩尔比(x=0.2,0.4,0.6和0.8)为原料合成了分散性较好的铌酸钾前驱体;然后将该前驱体通过化学拓扑反应制备出柱状的铌酸钾钠粉体;最后利用该粉体为原料,制备了铌酸钾钠陶瓷。测试结果表明,SrCO3的添加有利于形成分散性良好的铌酸钾前驱体;Sr含量对钨青铜结构前驱体到钙钛矿结构铌酸钾钠的相转变有显著影响:当x≤0.4时,前驱体全部转化为钙钛矿相;x>0.4时,前驱体转变不完全;x=0.8时,前驱体几乎未发生转变。x=0.4时,合成的铌酸钾钠颗粒为微米级,长径比约为12,具有较高的烧结活性,为织构陶瓷的制备提供了一种合适的模板籽晶。

The potassium-sodium niobate powders with columnar morphology were synthesized by two-step molten salt method, and the dense potassium sodium niobate ceramics were prepared. First, the potassium niobate precursors with good dispersibility were fabricated by using a small amount of KSr2 Nb 5 O15 powder as seeds and using the Nb2 O 5, KCl as well as SrCO 3 and Nb2 O 5 with different molar ratios ( x =0.2, 0.4, 0.6 and 0.8) as raw materials. Then, the columnar potassium-sodium niobate powders were prepared by chemical topological reaction of the precursor. Finally, the potassium sodium niobate ceramics were prepared by using the powders as raw materials. The results suggested that the addition of SrCO 3 was beneficial to the formation of a well-dispersed potassium niobate precursor. The content of Sr had a significant effect on the phase transition from the precursor of tungsten bronze structure to the potassium-sodium niobate with perovskite structure. When x ≤0.4, the precursor is completely converted to perovskite phase, and the transition was incomplete when x >0.4;at x =0.8, there was almost no change in the precursor. In the case of x =0.4, the synthesized potassium sodium niobate particles were of micron size and had a high sintering activity with an aspect ratio of about12, which provides a suitable template seed for the preparation of textured ceramics.