Rare earth-dependent trend of the glass transition activation energy of doped phosphate glasses: Calorimetric analysis

•Rare earth-doped barium phosphate glasses studied•Concurrent analysis of a family of heat flow data proposed•Glass transition activation energies assessed•Method for quantifying the intermediate-range order proposed•Glass transition correlation with rare earth ionic radii suggested

Eight types of rare earth (RE)-doped barium phosphate glasses have been studied by differential scanning calorimetry (DSC) in the glass transition region. Proposed is a concurrent analysis of a family of heat flow data assessing the glass transition activation energies. Furthermore, the DSC data indicate correlation of the activation energy with the ionic radius of the RE dopant, in agreement with the bond strength modifications suggested by the Raman data. Estimated activation energy values between 4.0(2) eV and 4.9(2) eV are in support of PO bond exchange theory of the glass transition. It is proposed that the measured activation energy can serve as a relative quantifier of the intermediate-range order of the glass structure.