The dependence of the firing conditions on the crystal structure formation of ZnGa2O4 has been investigated. The effects of temperature and atmosphere were examined and gave evidence of the instability of the zinc gallate under a reducing atmosphere at temperatures above 600 degrees C. A new preparation route has allowed to synthesize ZnGa2O4 at low temperature, right from 300 degrees C, avoiding the decomposition of the matrix during the annealing. Moreover, a different behavior under excitation has been observed for the phosphor prepared via this new route compared with the compound obtained by solid state reaction. A model, based on the optical behavior observed, is presented.