A multitechnique approach, consisting of x-ray diffraction, differential thermal analysis, low frequency Raman scattering from the acoustic vibrations of nanoclusters, and transmission electron microscopy associated with selected area diffraction, has been used to study the nucleation and crystallization processes in SiO ₂– Ga ₂ O ₃– K ₂ O glasses. The specific aim was to determine the structure and the size distribution of nanoparticles embedded in the glass matrix. It has been found that nearly spherical nanocrystals of β- Ga ₂ O ₃ , with a size of ∼2–3 nm, nucleate during thermal treatments at 900 °C. Crystallization was observed after annealing at higher temperature. The amount of the crystalline phase and the mean size of the nanocrystals increased with heat treatment, time and temperature. β- Ga ₂ O ₃ was the only crystalline phase to appear in all glass samples. © 2001 American Institute of Physics.