Fe3+ concentration dependence of photoacoustic absorption spectroscopy on ZnGa2O4 ceramic powders.

In this paper we present the photoacoustic spectroscopy of ZnGa2O4 with 5 and 10% of Fe3+. The ZnGa2O4 is a normal spinel, with Zn2+ ions in tetrahedral sites and Ga3+ ions in octahedral sites. It is expected for these hosts that Fe3+ ions occupy Ga3+ sites. Therefore, the optical properties would be associated to an octahedral symmetry. The energy levels were identified and the crystal field and electronic interaction parameters calculated with Tanabe-Sugano matrices for d5 configuration. We have also studied the dependence of the photoacoustic signal amplitude on the excitation light modulation frequency. Our results indicate that thermal expansion is the predominant phenomenon for the photoacoustic signal generation.