Disclosed is a synthesis process of a crystalline material with the CHA structure, which comprises the following steps: i) Preparation of a mixture that comprises one source of water, one source of a tetravalent element Y, one source of an alkaline or alkaline earth cation (A), one source of a trivalent element X, and one organic molecule (OSDA1) with the structure [R1R2R3R4N+]Q−, being the molar composition: n X2O3:YO2:a A:m OSDA1:z H2O, ii) crystallisation of the mixture obtained in i) in a reactor, iii) recovery of the crystalline material obtained in ii).