Thermal properties of a newly developed barium-iron-metaphosphate glass were investigated by means of differential scanning calorimetry (DSC) and thermal mechanical analysis (TMA). DSC data show the influence of iron ions on the glass transition temperature (T.,) and TMA shows that the glass transforms from the medium expansion material (12 X 10(-6)/degreesC for iron free glass) to low expansion glass. Infrared spectra were recorded as function of iron content on samples of the glass to investigate the glass structure. Infrared spectra show the presence of the P = O characteristic absorption band at 1277 cm(-1) in iron-free composition. This band seems to vanish with increasing, Fe2O3 content as P-O-Fe bonds replace the P-O-P bonds.