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.