Effects of MoO 3 , on Phase Separation of Na 2 O‐B 2 O 3 ‐SiO 2 Glasses

Immiscibility temperatures of Na 2 O‐B 2 O 3 ‐SiO glasses, with andwithout 1 mol% MoO 3 , additions, were determined and the effect of MoO 3 additions on the 65O°C immiscibility isotherms was established. In addition, immiscibility temperature and phase‐separation morphology of an Na 2 O‐B 2 O 3 ‐SiO 2 glass with progressive additions of MoO 3 , were investigated. It was found that the addition of small amounts of MoO 3 extends the immiscibility boundary of the system and raises the immiscibility temperature by ∼l8°C for each mol % MoO 3 , addition. Analysis of phase‐separation morphology suggests that the MoO 3 , additions do not significantly alter the tie lines of phase separation in the system, although such additions cause a lowering of the viscosities and the glass‐transition temperatures of these glasses.