Glasses in the RE₂O₃[Formula presented]₂O₃[Formula presented]₂(RE = Y, Nd, Yb, Dy, Ho and Sc) system were prepared using the melt-quench route. Prepared glasses were characterized using differential scanning calorimetry and differential thermal analyses to determine their glass transition temperatures, crystallisation temperatures, softening temperatures and specific heat. In-situ high temperature X-ray powder diffraction was used to study the crystals growth behaviour in these glasses from room temperature up to 1200 °C. Glasses were heat-treated at 1200 °C for 50 h to analyze the crystalline structures. X-ray diffraction studies were carried out to find the distribution of phases in these heat-treated samples. Qualitative and quantitative phase analyses were conducted using scanning electron microscopy combined with energy dispersive analysis. Moreover coefficients of thermal expansion, densities and refractive indices of these glasses were determined. It was found that transitions temperatures and crystalline structure morphology strongly depend on the type of rare-earth ions.