(155)Gd Mossbauer spectroscopic and X-ray diffraction study of the Zr(1-x)Gd(x)O(2) (-x/2) (0 < x <= 1-0) system

作者：Nakamura A^*; Otobe H; Wang J; Takeda M

来源：Journal of Physics and Chemistry of Solids, 2005, 66(2-4): 356-363.

DOI：10.1016/j.jpcs.2004.07.013

• oxide
• chemical synthesis
• Mossbauer spectroscopy
• X-ray diffraction
• crystal structure
• defect
• Moessbane effect

(155)Gd Mossbauer spectroscopy has been applied for the Gd(x)Zr(1-x)O(2-x/2) system, to elucidate the local structure around the Gd(3+) over the entire 0 < x < 1.0 range. Powder X-ray diffraction (XRD) measurements showed that below 1550 degrees C an intermediate pyrochlore (P) phase forms in the middle 0.45 <= x <= 0.55 range, sandwitched with a disordered defect-fluorite (F) phase on both sides (0.18 <= x <= 0.45 and 0.55 <= x <= 0.62), and upon heating above 1550 degrees C the former (P) is also disordered to the latter (F). (155)Gd-Mossbauer spectra in the solid solution region (0.18 <= x <= 0.62) apparently consisted of quadrupole split doublet which indicates the existence of one kind of distorted Gd site, in contrast to the well-resolved two doublets observed for the C-type Gd(2)O(3) (x = 1.0). (155)Gd-Mossbauer parameters in the solid solution region (0.18 <= x <= 0.62) such as electric quadrupole coupling constant (e(2)qQ), line width (2 Gamma) and relative absorption area (RAA) were found to exhibit a characteristic maximum around the ideal-pyrochlore composition (x = 0.50), while isomer shift (6) showed different behavior that this is nearly constant for 0.18 <= x <= 0.50 and increases slightly for x > 0.50. Their basic features were unchanged upon disordering above 1550 degrees C. These Mossbauer results suggest that the Gd(x)Zr(1-x)O(2-x/2) solid solution (0.18 <= x <= 0.62) has essentially a pyrochlore(P)-type local structure, whether long-range ordered or not, both the Gd-O bond strength and anisotropy attaining a maximum at x = 0.50.

• 出版日期2005-4