Photoluminescence and phosphorescence from different recombining centers in the Mn2þ-doped and
undoped Zn2GeO4 phosphors have been observed. By UV excitation the undoped sample presents a
broad band of blue–white emission from the host defects while the Mn-doped samples show both the
host and Mn2þ emissions with different phosphorescent durations. At the beginning of UV excitation
after the phosphorescence has been exhausted, the fluorescent time dependence of Mn2þ exhibits a fast
decay process to a constant intensity, different from the rising or charging process as the typical behavior
for the common persistent phosphors. This unusual behavior was studied using electron paramagnetic
resonance (EPR) spectroscopy. A decrease of the EPR signal from Mn2þ was found for the sample under
UV irradiation, suggesting the occurrence of ionization of Mn2þ to Mn3þ. A slow recovering process of
the ionization has also been detected, which is consistent with the observation of phosphorescence from
Mn2þ doped samples.