Abstract
The phase diagram of the ZrO 2-Nd 2O 3 system has been characterized showing isolated two-phase regions for a cubic fluorite-type ZrO 2 solid solution and Nd 2Zr 2O 7 with a pyrochlore-type structure. A thermodynamic analysis was carried out to elucidate the origin of this interesting phase equilibrium. A compound energy model with the formula (Zr 4+,Nd 3+) 0.5(Nd 3+,Zr 4+) 0.3(O 2-,va) 2 was applied to describe the Gibbs energy for these phases in consideration of the ordering of the cation sites in the structure. The ordering arrangement on the anion sites was not taken into account. The Gibbs energy for the liquid was described using an ionic solution model, while the binary compounds, such as tetragonal and monoclinic ZrO 2, and cubic and hexagonal Nd 2O 3, were treated as stoichiometric solid phases. The thermodynamic assessment was based on the experimental phase boundaries as well as the evaluated formation energy for the stoichiometric Nd 2Zr 2O 7 phase. The phase diagram calculations showed that the peculiar feature of this phase diagram was reproduced well in our work. The results strongly suggest that the two-phase boundaries between the cubic fluorite-type ZrO 2 solid solution and the pyrochlore-type structure occur due to the ordering of the Zr 4+ and Nd 3+ cations.
| Original language | English |
|---|---|
| Pages (from-to) | 1167-1174 |
| Number of pages | 8 |
| Journal | Materials Transactions |
| Volume | 46 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 2005 Jun |
| Externally published | Yes |
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Keywords
- Calculation of phase diagrams (CALPHAD) method
- Order-disorder transition
- Pyrochlore structure
- Thermodynamic analysis
- Zirconia ceramics
ASJC Scopus subject areas
- Materials Science(all)
- Metals and Alloys
Cite this
Equilibrium between fluorite and pyrochlore structures in the ZrO 2-Nd 2O 3 system. / Ohtani, Hiroshi; Matsumoto, Satoshi; Sundman, Bo; Sakuma, Taketo; Hasebe, Mitsuhiro.
In: Materials Transactions, Vol. 46, No. 6, 06.2005, p. 1167-1174.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Equilibrium between fluorite and pyrochlore structures in the ZrO 2-Nd 2O 3 system
AU - Ohtani, Hiroshi
AU - Matsumoto, Satoshi
AU - Sundman, Bo
AU - Sakuma, Taketo
AU - Hasebe, Mitsuhiro
PY - 2005/6
Y1 - 2005/6
N2 - The phase diagram of the ZrO 2-Nd 2O 3 system has been characterized showing isolated two-phase regions for a cubic fluorite-type ZrO 2 solid solution and Nd 2Zr 2O 7 with a pyrochlore-type structure. A thermodynamic analysis was carried out to elucidate the origin of this interesting phase equilibrium. A compound energy model with the formula (Zr 4+,Nd 3+) 0.5(Nd 3+,Zr 4+) 0.3(O 2-,va) 2 was applied to describe the Gibbs energy for these phases in consideration of the ordering of the cation sites in the structure. The ordering arrangement on the anion sites was not taken into account. The Gibbs energy for the liquid was described using an ionic solution model, while the binary compounds, such as tetragonal and monoclinic ZrO 2, and cubic and hexagonal Nd 2O 3, were treated as stoichiometric solid phases. The thermodynamic assessment was based on the experimental phase boundaries as well as the evaluated formation energy for the stoichiometric Nd 2Zr 2O 7 phase. The phase diagram calculations showed that the peculiar feature of this phase diagram was reproduced well in our work. The results strongly suggest that the two-phase boundaries between the cubic fluorite-type ZrO 2 solid solution and the pyrochlore-type structure occur due to the ordering of the Zr 4+ and Nd 3+ cations.
AB - The phase diagram of the ZrO 2-Nd 2O 3 system has been characterized showing isolated two-phase regions for a cubic fluorite-type ZrO 2 solid solution and Nd 2Zr 2O 7 with a pyrochlore-type structure. A thermodynamic analysis was carried out to elucidate the origin of this interesting phase equilibrium. A compound energy model with the formula (Zr 4+,Nd 3+) 0.5(Nd 3+,Zr 4+) 0.3(O 2-,va) 2 was applied to describe the Gibbs energy for these phases in consideration of the ordering of the cation sites in the structure. The ordering arrangement on the anion sites was not taken into account. The Gibbs energy for the liquid was described using an ionic solution model, while the binary compounds, such as tetragonal and monoclinic ZrO 2, and cubic and hexagonal Nd 2O 3, were treated as stoichiometric solid phases. The thermodynamic assessment was based on the experimental phase boundaries as well as the evaluated formation energy for the stoichiometric Nd 2Zr 2O 7 phase. The phase diagram calculations showed that the peculiar feature of this phase diagram was reproduced well in our work. The results strongly suggest that the two-phase boundaries between the cubic fluorite-type ZrO 2 solid solution and the pyrochlore-type structure occur due to the ordering of the Zr 4+ and Nd 3+ cations.
KW - Calculation of phase diagrams (CALPHAD) method
KW - Order-disorder transition
KW - Pyrochlore structure
KW - Thermodynamic analysis
KW - Zirconia ceramics
UR - http://www.scopus.com/inward/record.url?scp=23744510954&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=23744510954&partnerID=8YFLogxK
U2 - 10.2320/matertrans.46.1167
DO - 10.2320/matertrans.46.1167
M3 - Article
AN - SCOPUS:23744510954
VL - 46
SP - 1167
EP - 1174
JO - Materials Transactions
JF - Materials Transactions
SN - 1345-9678
IS - 6
ER -