The optimal temperature regime for the synthesis of glass ceramics with YNbO4:Tb3+ crystalline inclusions has been established. Glass ceramics were synthesized on the basis of a sodium borate matrix from oxide precursors. It has been established that synthesis at a temperature of 950°C is optimal, since at this temperature only one crystalline phase YNbO4:Tb3+ is formed in the glass and its content is maximum. The spectra of crystalline inclusions and the glass matrix were obtained by the method of local cathodoluminescence, the phase composition of glass ceramics was studied by X-ray phase analysis.