The effects of phosphorus pentoxide additions on the thermal, rheological, and structural properties of sodium borosilicate glass

•The solubility limit of phosphorus pentoxide in a sodium borosilicate glass was between 3 and 4 mol%.•BS-SEM suggested phosphorus pentoxide induced nucleation-type phase separation.•Phosphorus pentoxide increased and decreased the glass transition temperature.•Phosphorus pentoxide increased viscosity at lower temperatures.•Raman spectroscopy suggested phosphorus pentoxide re-polymerised the glass network.