74.
Mg
xZn
1−xO is a promising alloy system with UV-tunable bandgap. The alloy can have the hexagonal or cubic structure depending on the
composition x and growth conditions. We present studies of the optical and material properties of Mg
0.1Zn
0.9O and Mg
0.6Zn
0.4O sintered ceramics. The rationale for choosing these compositions is that alloys of both the wurtzite and the cubic phases,
respectively, can be investigated. To study the alloying dynamics for the optimization of light emission, the properties as
a function of annealing temperature in the range of 600–1,100 °C were investigated via micro-photoluminescence, X-ray diffraction,
and imaging techniques. For the Mg
0.1Zn
0.9O it was found that a threshold temperature of ~900 °C is required in order to initiate the formation of the solid solution
with the wurtzite structure. At the elevated temperature regime, the photoluminescence energy for this ceramic sample shifted
from 3.25 to 3.5 eV, while the ceramic retained the wurtzite structure. The Mg
0.6Zn
0.4O was found to have a sequence of phases: initially the alloy formed with the wurtzite structure, and then a transition into
the NaCl cubic structure took place. Similar to the Mg
0.1Zn
0.9O, a threshold temperature of ~900 °C was required in order to initiate the alloying process. At that temperature regime an
alloy was formed with the wurtzite structure, and its photoluminescence energy was ~3.25 eV. At ~1,100 °C the alloy was found
to undergo a phase transition from wurtzite to cubic structure. The photoluminescence energy at that temperature was considerably
shifted into the UV-range of 4 eV.
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