Structural variation and optical properties of ZnO–LiGaO2 pseudo-binary system

The structural variation in the x(LiGaO2)1/2(1−x)ZnO alloy system was studied by powder XRD, TEM-SAD and Raman spectroscopy. It was elucidated that the phase varied upon increasing the alloying level was the wurtzite-type for 0≤x<0.2, the Zn2LiGaO4-type for 0.2≤x≤0.5 and the β-LiGaO2-type for 0.8≤x≤1, and the 0.5<x<0.8 region was the immiscible region of ZnO with LiGaO2. The solubility limit of LiGaO2 in ZnO was explained by the c0/a0 ratio based on the fact that there is no binary wurtzite phase for a c0/a0 less than 1.6. The optical phonons of wurtzite and its derived phase were simply explained by the lattice shrinkage and reduced mass upon reduction the alloying of ZnO with LiGaO2. The bowing parameter of the optical band gap of y(Zn2LiGaO4)1/4(1−y)ZnO was determined to be 0.67 eV. The value was very low, and it was related to the small lattice and chemical mismatches between the Zn2LiGaO4 and ZnO. - Graphical abstract: The structure of ZnO varied upon alloying with LiGaO2. Highlights: ► We studied structural variation in the x(LiGaO2)1/2(1−x)ZnO alloy system. ► The wurtzite- and its related Zn2LiGaO4-type phase appeared for 0≤x≤0.5. ► The solubility limit of LiGaO2 in ZnO was related to the wurtzite c0/a0 ratio. ► The energy band gap of ZnO was widened up to 4.04 keV by the alloying with LiGaO2. ► The bowing parameter of y(Zn2LiGaO4)1/4(1−y)ZnO was determined to be 0.67 eV.