Physical properties in nanosized Zn0.97Al0.03O powders under high pressure by in-situ angular dispersive X-ray diffraction
Chih-Ming Lin1*, Hsin-Tzu Liu2,3, Shi-Yao Zhong1, Chia-Hung Hsu1, Yi-Te Chiu1, Ming-Fong Tai4, Jenh-Yih Juang5, Yu-Chun Chuang6, Yen-Fa Liao6
1Applied Science, National Hsinchu University of Education, Hsinchu, Taiwan
2Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan
3Chemical Systems Research Division, Chung-Shan Institute of Science & Technology, Taoyuan, Taiwan
4Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
5Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
6National Synchrotron Radiation Research Center, Hsinchu, Taiwan
* presenting author:Chih-Ming Lin,
Nanosized aluminum-doped zinc oxide Zn0.97Al0.03O (AZO) powders in both plate-like and granular shapes were synthesized by chemical precipitation method. Zinc nitrate and aluminum nitrate were used as reactants and urea was used as the precipitating agent for obtaining the precursor. The thermogravimetric (TG) analysis indicated that precursor was converted to oxide from hydroxide near about 250oC. The precursor was then heated to 500oC and was calcined at 500oC for three hours. The structure and morphology of the products were measured and characterized by angular dispersive X-ray diffraction (ADXRD) and scanning electron microscopy (SEM). ADXRD results showed that AZO nano-powders (AZO-NPs) exhibited würtzite zinc oxide structure and there was no other discernible impurity phase, indicating that Al atoms were doped into the zinc oxide lattice by substituting for zinc atoms. The grain size of AZO-NPs was estimated to be about 21.4 nm with morphology of plate-like and granular shapes. The in situ ADXRD measurements indicated that, for loading run, the pressure-induced würtzite (B4)-to-rocksalt (B1) structural phase transition began at 9.0(1) GPa. Compared to the predicted phase-transition pressure of 12.7 GPa for pristine ZnO nanocrystals of similar size (21.4 nm), the transition pressure for the present AZO-NPs exhibited a reduction of 3.7 GPa. The significant reduction in phase-transition pressure is attributed to the effects of highly selective site occupation, namely Zn2+ and Al3+ were mainly found in tetrahedral and octahedral sites, respectively.

Keywords: nanosized aluminum-doped zinc oxide , zinc-blende, phase transition, angular-dispersive X-ray diffraction