Abstract
The crystal structure of 3 at.% and 9 at.% Si-doped HfO2 powder was determined through refinements using X-ray and neutron diffraction patterns. The lattice parameters, atomic positions, dopant occupancy, and the second phase fraction were determined with high precision using a combined full pattern fitting via the Rietveld method. The results show that both 3 at.% and 9 at.% Si-doped HfO2 powder exhibit the monoclinic crystal structure with P 1 21/c 1 space group. Through the combined refinement, the crystal structure parameters, especially for the positions and occupancies of the lighter atoms, were more precisely determined compared to independent X-ray diffraction refinement. Although the ionic radius of Si4+ is smaller than Hf4+, with increasing Si occupancy, the unit cell volume slightly increases; possible mechanisms for this effect are discussed. Moreover, the refined results provide evidence of the existence of a non-equilibrium phase of HfxSi1-xO2. The second phase (SiO2) fraction is determined as 0.17 at.% for 3 at.% Si-doped HfO2 powders and 1.7 at.% for 9 at.% Si-doped HfO2 powders.
Original language | English |
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Pages (from-to) | 655-661 |
Number of pages | 7 |
Journal | Journal of Alloys and Compounds |
Volume | 646 |
DOIs | |
State | Published - Jul 2 2015 |
Externally published | Yes |
Funding
Use of the Advanced Photon Source (APS) was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences , under Contract No. DEAC02-06CH11357 . The authors acknowledge contributions from Matthew Suchomel at the APS for assistance with measurements. The authors are also grateful to Dr. Cai Qingsheng at North Carolina State University for help with the neutron diffraction measurement. L.L. Zhao wants to thank the financial support provided by Shaanxi Key Engineering Program ( 2012GY2-36 ). J.S.F. and J.J. acknowledge support from the U.S. Department of the Army under Grant No. W911NF-09-1-0435 .
Keywords
- Crystal structure
- Neutron diffraction
- Rietveld refinement
- X-ray diffraction