The
mechanoluminescence response of oxide materials has implications
for the use of these materials in structural health monitoring applications,
where crack propagation needs to be monitored. Thus, we describe the
mechanoluminescence of MgO powders, showing that the signal is dependent
on the existence of oxygen vacancies. Cathodoluminescence (CL) spectra
of the powders exhibited an emission at 2.10 eV associated with F
+ centers (oxygen vacancies), as well as intense
CL emissions at 3.70 and 4.10 eV, associated with M
+ and M
– centers (paired-oxygen
vacancies). Furthermore, CL measurements revealed an emission at 1.70
eV, which was not influenced by mechanical stress and can be attributed
to an electronic transition between excited and ground F
+ states. The presence of oxygen vacancies was confirmed
by X-ray photoelectron spectroscopy and electron energy loss spectroscopy.
Measurements of CL intensity with respect to electron irradiation
time confirmed the presence of high amounts of F
+ centers, as well as a saturation time effect in which emission
intensity achieves a maximum only after a certain time of irradiation.
The existence of this saturation effect was correlated to the mechanoluminescence
signal.