The preparation and properties of hexagonal strontium-yttrate-silicate apatite (SrY 4 [SiO 4 ] 3 O, space group P6 3 /m) as the main product of sinter-crystallization process, in which the non-equilibrium melt was formed in the temperature interval from 1300 to 1550°C in the SrO-Y 2 O 3 -SiO 2 system is described in this work. The formation of non-equilibrium melt is facilitated by borate fluxes, alkaline fluxes and talc. The apparent activation energy and the frequency factor of the sinter-crystallization process were determined to be 1525kJ·mol −1 and 1.04·10 45 s −1 , respectively. The material shows low value of linear thermal expansion coefficient of (1.1±0.1)·10 −6 °C −1 in the temperature range from 25 to 850°C. The important feature of this compound is the formation of colored center after the exposition to X-ray radiation hence prepared material is an important candidate for optical applications, sensors and dosimeters.