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Materials (Basel). 2016 Jul 12;9(7). pii: E561. doi: 10.3390/ma9070561.

Structural Transitions in Nanosized Zn0.97Al0.03O Powders under High Pressure Analyzed by in Situ Angle-Dispersive X-ray Diffraction.

Author information

1
Department of Applied Science, National Hsinchu University of Education, Hsinchu 30014, Taiwan. cmlin@mail.nhcue.edu.tw.
2
Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan. missliu29@yahoo.com.tw.
3
Chemical Systems Research Division, Chung-Shan Institute of Science & Technology, Taoyuan 32546, Taiwan. missliu29@yahoo.com.tw.
4
Department of Applied Science, National Hsinchu University of Education, Hsinchu 30014, Taiwan. g9925056@mail.nhcue.edu.tw.
5
Department of Applied Science, National Hsinchu University of Education, Hsinchu 30014, Taiwan. g10025051@mail.nhcue.edu.tw.
6
Department of Applied Science, National Hsinchu University of Education, Hsinchu 30014, Taiwan. vinnychiu0109@gmail.com.
7
Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan. mftai@phys.nthu.edu.tw.
8
Department of Electrophysics, National Chiao Tung University, Hsinchu 33013, Taiwan. jyjuang@g2.nctu.edu.tw.
9
National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan. chuang.yc@nsrrc.org.tw.
10
National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan. liao.yenfa@nsrrc.org.tw.

Abstract

Nanosized aluminum-doped zinc oxide Zn1-xAlxO (AZO) powders (AZO-NPs) with x = 0.01, 0.03, 0.06, 0.09 and 0.11 were synthesized by chemical precipitation method. The thermogravimetric analysis (TGA) indicated that the precursors were converted to oxides from hydroxides near 250 °C, which were then heated to 500 °C for subsequent thermal processes to obtain preliminary powders. The obtained preliminary powders were then calcined at 500 °C for three hours. The structure and morphology of the products were measured and characterized by angle-dispersive X-ray diffraction (ADXRD) and scanning electron microscopy (SEM). ADXRD results showed that AZO-NPs with Al content less than 11% exhibited würtzite zinc oxide structure and there was no other impurity phase in the AZO-NPs, suggesting substitutional doping of Al on Zn sites. The Zn0.97Al0.03O powders (A₃ZO-NPs) with grain size of about 21.4 nm were used for high-pressure measurements. The in situ ADXRD measurements revealed 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 grain size (~21.4 nm), the transition pressure for the present A₃ZO-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:

aluminum-doped zinc oxide; angle-dispersive X-ray diffraction; phase transition; zinc-blende

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