SrNb2O6-NaNbO3-LiNbO3赝三元系相图的研究

本文用X射线衍射、热处理及差热分析等方法测定了SrNb₂O₆-NaNbO₃-LiNbO₃赝三元系的室温截面及相应的SrNb₂O₆-NaNbO₃,SrNb₂O₆-LiNbO₃和NaNbO₃-LiNbO₃等三个赝二元系相图;粗略地研究了Sr_0.42Na_0.16NbO₃-LiNbO₃系的纵截面;含5mol％LiNbO₃及10mol％LiNbO₃的SrNb₂O₆-NaNbO₃的纵截面。确定了室温Sr₂Na(NbO₃)₅(以下略为S₂N)相为四方钨青铜结构。其点阵常数为a=12.36?,c=3.906?.LiNbO₃在S₂N相内的溶解度可达～10mol％,当LiNbO₃含量超过5mol％时,S₂N相畸变为S₂N′相。S₂N′相为正交晶系。实验确定室温S₂N(S₂N′)相系亚稳相。在900-1100℃长时间退火即分解为SrNb₂O₆和以NaNbO₃为基的固溶体的混合物。 关键词：

INVESTIGATION OF THE PSEUDO-TERNARY SYSTEM SrNb2O6-NaNbO3-LiNbO3

The pseudo-ternary system SrNb₂O₆-NaNbO₃-LiNbO₂ has been investigated by means of DTA, heat treatment and X-ray diffraction techniques. It has been found that at room temperature Sr₂Na(NbO₃)₅(S₂N) is a metastable intermediate compound which has a tetragonal tungsten-bronze structure with a=12.36?, c=3.906?. LiNbO₃ can be dissolved in S₂N up to a limit about 10 mol% ; and in the range of 5-10mol% of LiNbO₃, the S₂N phase is distorted into S₂N′, which belongs to the orthorhombic system and is also a metastable phase. After long time annealing at 900-1100℃, the metastable phases S₂N, S₂N′ will decompose into a mixture of SrNb₂O₆ and a phase of solid solution based on NaNbO₃. The phase diagram of the corresponding binary systems and the isothermal section of the pseudo-ternary system have been established.
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