The temperature-dependent lifetime of trivalent cerium was determined in (Y1-x Ce (x) )(3)Al2.5Ga2.5O12 (where x = 0.1 and 0.2) over a temperature range of 20-120 A degrees C. In both samples, the quenching temperature is significantly lower compared to (Y1-x Ce (x) )(3)Al5O12. The difference in quenching temperatures is explained by evaluating the changes in the lattice, which occur as a result of substituting the Al3+ for Ga3+. The information presented in this report is useful for future design of phosphors for use as non-contact temperature sensors.