Structural variation and optical properties of ZnO-LiGaO ₂ pseudo-binary system

The structural variation in the x(LiGaO ₂) _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 Zn ₂LiGaO ₄-type for 0.2≤x≤0.5 and the β-LiGaO ₂-type for 0.8≤x≤1, and the 0.5<x<0.8 region was the immiscible region of ZnO with LiGaO ₂. The solubility limit of LiGaO ₂ in ZnO was explained by the c ₀/a ₀ ratio based on the fact that there is no binary wurtzite phase for a c ₀/a ₀ 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 LiGaO ₂. The bowing parameter of the optical band gap of y(Zn ₂LiGaO ₄) _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 Zn ₂LiGaO ₄ and ZnO.