The present disclosure relates to a process for fabricating a crystalline scintillator material with a structure of elpasolite type of theoretical composition A2BC(1-y)MyX(6-y) wherein:A is chosen from among Cs, Rb, K, Na,B is chosen from among Li, K, Na,C is chosen from among the rare earths, Al, Ga,M is chosen from among the alkaline earths,X is chosen from among F, Cl, Br, I,y representing the atomic fraction of substitution of C by M and being in the range extending from 0 to 0.05, comprising its crystallization by cooling from a melt bath comprising r moles of A and s moles of B, the melt bath in contact with the material containing A and B in such a way that 2s / r is above 1. The process shows an improved fabrication yield. Moreover, the crystals obtained can have compositions closer to stoichiometry and have improved scintillation properties.