# O–Y system

> O–Y system: 40 accepted literature values (phase transition 17, invariant reaction 10, heat capacity / entropy / enthalpy 7, crystal structure 3) and 0 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

HTML: https://data.orchid-project.org/systems/O-Y.html · Markdown: https://data.orchid-project.org/systems/O-Y.md

40 accepted literature values from 3 paper(s) (experimental 24, model 14, unspecified 2); 0 calculated phase diagram(s). 9 further extracted value(s) not accepted by the reader-agreement checks are only in the JSON/CSV.

Data: [JSON](https://data.orchid-project.org/literature/systems/O-Y.json) · [CSV](https://data.orchid-project.org/systems/O-Y.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#O-Y) · [phases (10)](https://data.orchid-project.org/phases/pages/O-Y.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/O-Y.html) · [Markdown](https://data.orchid-project.org/systems/O-Y.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 24 |
| model | 14 |
| unspecified | 2 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 10 |
| phase transition | 17 |
| formation | 1 |
| heat capacity / entropy / enthalpy | 7 |
| crystal structure | 3 |
| other property | 2 |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/O/O-Y.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/O/O-Y.json) · [CALPHAD hull YO-04Che](https://data.orchid-project.org/hulls/calphad-sgte/O/O-Y--YO-04Che.json) · [CALPHAD hull YO-05Che](https://data.orchid-project.org/hulls/calphad-sgte/O/O-Y--YO-05Che.json) · [CALPHAD hull YO-07Dju](https://data.orchid-project.org/hulls/calphad-sgte/O/O-Y--YO-07Dju.json) · [CALPHAD hull YO-96Gro](https://data.orchid-project.org/hulls/calphad-sgte/O/O-Y--YO-96Gro.json) · [CALPHAD hull YO-98Swa-LB](https://data.orchid-project.org/hulls/calphad-sgte/O/O-Y--YO-98Swa-LB.json) · [CALPHAD hull YO-98Swa-orig](https://data.orchid-project.org/hulls/calphad-sgte/O/O-Y--YO-98Swa-orig.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the O–Y system (10)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 4921 | congruent melting: L\* -> gas\* (P = 1 bar) | L: O 0.371; gas: O 0.371 | model | [1] Djurovic 2007 | Table 2, p. 6, row 10; `ORC-PI4HG6R7AE` |  |
| 2718 | congruent melting: L\* -> β-Y2O3\* | L: O 0.598; β-Y2O3: O 0.598 | model | [1] Djurovic 2007 | Table 2, p. 6, row 8; `ORC-TGDU6KQWJG` |  |
| 2712 | congruent melting: L\* -> β-Y2O3\* | L: O 0.6, Y 0.4; β-Y2O3: O 0.6, Y 0.4 | experimental | [1] Djurovic 2007; _cites Foex 1977_ | Table 2, p. 6, row 9; `ORC-7MJDZGWJ4C` |  |
| 2600 | other: β-Y2O3\* -> α-Y2O3 + L | β-Y2O3: O 0.588; α-Y2O3: O 0.6, Y 0.4 | model | [1] Djurovic 2007 | Table 2, p. 6, row 7; `ORC-O36GKKQCAS` |  |
| 1943 | congruent melting: L\* -> β-Y\* | L: O 0.226; β-Y: O 0.226 | experimental | [1] Djurovic 2007; _cites Tucker 1964_ | Table 2, p. 6, row 6; `ORC-BX7ZQICMLR` |  |
| 1943 | congruent melting: L\* -> β-Y\* | L: O 0.23; β-Y: O 0.23 | model | [1] Djurovic 2007 | Table 2, p. 6, row 5; `ORC-TOSKZQ7MDN` |  |
| 1833 | eutectic: L\* -> β-Y + gα-Y2O3 | L: O 0.373; gα-Y2O3: O 0.6, Y 0.4 | model | [1] Djurovic 2007 | Table 2, p. 6, row 3; `ORC-7ARCVKY5MQ` |  |
| 1833 | eutectic: L\* -> β-Y + gα-Y2O3 | L: O 0.373; gα-Y2O3: O 0.6, Y 0.4 | experimental | [1] Djurovic 2007; _cites Tucker 1964_ | Table 2, p. 6, row 4; `ORC-EZMSYUMRIE` |  |
| 1453 | eutectoid: β-Y\* -> α-Y + gα-Y2O3 | β-Y: O 0.18; gα-Y2O3: O 0.6, Y 0.4 | model | [1] Djurovic 2007 | Table 2, p. 6, row 1; `ORC-QBIS6KJNXV` |  |
| 1453 | eutectoid: β-Y\* -> α-Y + gα-Y2O3 | β-Y: O 0.18; gα-Y2O3: O 0.6, Y 0.4 | experimental | [1] Djurovic 2007; _cites Tucker 1964_ | Table 2, p. 6, row 2; `ORC-TKL4ZIVLII` |  |

## Formation enthalpies

Literature values in kJ/mol-atom where the per-atom basis is known. DFT columns: the lowest-energy entry at the same composition (Materials Project 2026.04.13, OQMD v1.8; different energy references, never averaged), from [dft_parity.json](https://data.orchid-project.org/literature/dft_parity.json).

Table: Enthalpies of formation, O–Y system (1)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| C-Y2O3 | [Y2O3](https://data.orchid-project.org/compounds/Y2O3.html) | -386.56 kJ/mol-atom | 298.15 | model | -383.134 (mp-aaaaadya) | -367.434 (oqmd-3427) | [2] ZINKEVICH 2007 | Table 6.1, p. 24, row 7; `ORC-ZSQUMYSJBZ.0f301d` |  |

## Other properties

### Phase transition (17)

Table: Phase transition, O–Y system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 298.15 K | 298.15 | polymorphic: B ⇒ A; _alloy: O 0.6, Y 0.4_ | unspecified | [2] ZINKEVICH 2007; _cites Ma 2002_ | Table 2.3, p. 10, row 8; `ORC-77D6Y6WR4L` |  |
| Phase transition | 298.15 K | 298.15 | polymorphic: B ⇒ A; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Husson 1999_ | Table 2.3, p. 10, row 7; `ORC-T7RFWYJ2MV` |  |
| Phase transition | 298.15 K | 298.15 | polymorphic: C ⇒ B; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Husson 1999_ | Table 2.3, p. 10, row 5; `ORC-3BFLHAF43H` |  |
| Phase transition | 298.15 K | 298.15 | polymorphic: C ⇒ B; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Atou 1990_ | Table 2.3, p. 10, row 4; `ORC-AGPMNQWHF7` |  |
| Phase transition | 298.15 K | 298.15 | polymorphic: C ⇒ B; _alloy: O 0.6, Y 0.4_ | unspecified | [2] ZINKEVICH 2007; _cites Ma 2002_ | Table 2.3, p. 10, row 6; `ORC-HGLVJ5ZQO3` |  |
| Phase transition | 1273 K | 1273 | polymorphic: C ⇒ B; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Hoekstra 1966_ | Table 2.3, p. 10, row 3; `ORC-NI4FCDDDW6` |  |
| Phase transition | 2512 K | 2512 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Swamy 1999_ | Table 2.1, p. 6, row 9; `ORC-5ZYTMGE47H` |  |
| Phase transition | 2565 K | 2565 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Adylov 1987_ | Table 2.1, p. 6, row 6; `ORC-Q5FXAB2P5X` |  |
| Phase transition | 2573 K | 2573 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Coutures 1976_ | Table 2.1, p. 6, row 2; `ORC-77ASUSLLGU` |  |
| Phase transition | 2573 K | 2573 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Glushkova 1988_ | Table 2.1, p. 6, row 7; `ORC-QAZT3KZOCR` |  |
| Phase transition | 2581 K | 2581 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Navrotsky 2005_ | Table 2.1, p. 6, row 10; `ORC-44KJOG7SCJ` |  |
| Phase transition | 2583 K | 2583 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Foex 1966_ | Table 2.1, p. 6, row 1; `ORC-WMGNFWXDNV` |  |
| Phase transition | 2600 K | 2600 | polymorphic: C \<=> H; _alloy: O 0.6, Y 0.4_ | model | [2] ZINKEVICH 2007 | Table 2.2, p. 8, row 20; `ORC-GLU6TQ3NER` |  |
| Phase transition | 2600 K | 2600 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Shpilrain 1976_ | Table 2.1, p. 6, row 5; `ORC-HQMKJXHRCI` |  |
| Phase transition | 2623 K | 2623 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Andrievskaya 1997_ | Table 2.1, p. 6, row 8; `ORC-EE23IH5G5K` |  |
| Phase transition | 2623 K | 2623 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Tresvyatkii 1971_ | Table 2.1, p. 6, row 3; `ORC-EOXIXWMGYI` |  |
| Phase transition | 2663 K | 2663 | polymorphic: C ⟺ H; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Shevtchenko 1985_ | Table 2.1, p. 6, row 4; `ORC-SAKLIIWPQP` |  |

### Heat capacity / entropy / enthalpy (7)

Table: Heat capacity / entropy / enthalpy, O–Y system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy; _printed: ΔS_ | 4.08 J mol^-1 K^-1 |  | UNKNOWN; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Hoekstra 1966_ | Table 5.1, p. 18, row 2; `ORC-MGNLR57VUY.e5876c` |  |
| Entropy; _printed: ΔS_ | 4.08 J mol−1 K−1 |  | Y2O3; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Hoekstra 1966_ | Table 5.1, p. 18, row 2; `ORC-MGNLR57VUY.200bc8` |  |
| Entropy; _printed: °S_ | 98.96 unknown | 298.15 | C-Y2O3; _alloy: O 0.6, Y 0.4_ | model | [2] ZINKEVICH 2007 | Table 6.1, p. 24, row 7; `ORC-ZSQUMYSJBZ.1e0924` |  |
| Entropy; _printed: ΔS_ | 18.5 J mol^-1 K^-1 | 2581 | UNKNOWN; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Navrotsky 2005_ | Table 5.1, p. 18, row 4; `ORC-CGSTJXPOW5.ba0a69` |  |
| Entropy; _printed: ΔS_ | 18.5 J mol−1 K−1 | 2581 | Y2O3; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Navrotsky 2005_ | Table 5.1, p. 18, row 4; `ORC-CGSTJXPOW5.b64de2` |  |
| Entropy; _printed: ΔS_ | 9.654 J mol^-1 K^-1 | 2600 | UNKNOWN; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Shpilrain 1976_ | Table 5.1, p. 18, row 3; `ORC-HRI6SIPIVS.b1ecf4` |  |
| Entropy; _printed: ΔS_ | 9.654 J mol−1 K−1 | 2600 | Y2O3; _alloy: O 0.6, Y 0.4_ | experimental | [2] ZINKEVICH 2007; _cites Shpilrain 1976_ | Table 5.1, p. 18, row 3; `ORC-HRI6SIPIVS.a5b718` |  |

### Crystal structure (3)

Table: Crystal structure, O–Y system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| lattice molar volume | 40.385 cm3 mol-1 | 298.15 | Y2O3 (A-type); _alloy: O 0.6, Y 0.4_ | model | [2] ZINKEVICH 2007 | Table 3.1, p. 12, row 2; `ORC-Y7SEHDV3F3.1b8f79` |  |
| lattice molar volume | 41.132 cm3 mol-1 | 298.15 | Y2O3 (B-type); _alloy: O 0.6, Y 0.4_ | model | [2] ZINKEVICH 2007 | Table 3.1, p. 12, row 2; `ORC-Y7SEHDV3F3.cea032` |  |
| lattice molar volume | 44.804 cm3 mol-1 | 298.15 | Y2O3 (C-type); _alloy: O 0.6, Y 0.4_ | model | [2] ZINKEVICH 2007 | Table 3.1, p. 12, row 2; `ORC-Y7SEHDV3F3.fae386` |  |

### Other property (2)

Table: Other property, O–Y system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Other; _printed: transition enthalpy_ | 19 kJ mol 21 | 2600 | a-Y2O3 | model | [3] Swamy 1998 | p. 3; `ORC-MEWYU5NTOW` | “This corresponds to a transition enthalpy of 19 kJ mol 21 at → b2600 K, the transition temperature taken here for a ← Y 2 O 3 .” |
| Other; _printed: enthalpy_ | 68 kJ mol 21 | 2712 |  | model | [3] Swamy 1998 | p. 3; `ORC-PPZ4BO726P` | “For a melting temperature of 2712 K taken here for yttria, the Wu and Pelton entropy would translate to an enthalpy value of about 68 kJ mol 21 .” |

## Sources

Reporting papers the values were read from (a value cited from another work names that work in its row).

1. Dejan Djurovic, Matvei Zinkevich, Fritz Aldinger, Thermodynamic modeling of the yttrium–oxygen system, Calphad 31, 560-566 (2007). [doi:10.1016/j.calphad.2007.01.010](https://doi.org/10.1016/j.calphad.2007.01.010)
2. M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007). [doi:10.1016/j.pmatsci.2006.09.002](https://doi.org/10.1016/j.pmatsci.2006.09.002)
3. Varghese Swamy, Hans J. Seifert, Fritz Aldinger, Thermodynamic properties of Y2O3 phases and the yttrium–oxygen phase diagram, Journal of Alloys and Compounds 269, 201-207 (1998). [doi:10.1016/s0925-8388(98)00245-x](https://doi.org/10.1016/s0925-8388%2898%2900245-x)

## Please cite

- R. Arróyave, J. Saal, D. Shin, ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/10.5281/zenodo.23735569
- R. Arróyave, J. Saal, D. Shin, ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD) (version 2026.10), Zenodo (2026). https://doi.org/10.5281/zenodo.23735891
- R. Arróyave, J. Saal, D. Shin, ORCHID data: umbrella record of the ORCHID datasets (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/10.5281/zenodo.23736065

Also cite the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work); A. Jain et al., The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1 (2013) 011002, https://doi.org/10.1063/1.4812323 (CC BY 4.0); J. E. Saal et al., JOM 65 (2013) 1501, https://doi.org/10.1007/s11837-013-0755-4 and S. Kirklin et al., npj Comput. Mater. 1 (2015) 15010, https://doi.org/10.1038/npjcompumats.2015.10 (CC BY 4.0); B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, https://doi.org/10.1016/j.calphad.2025.102833 (CC BY 4.0), and the original assessment named in each file.

Version 1, machine-extracted: values were read by language-model readers constrained to quote their source and checked automatically, and the release was then audited on the printed pages by adversarial audits, an independent second review of fit-facing records and a preliminary human review of a frozen sample. Flags such as accepted and ESPEI-ready record screening results, not certification; known issues are listed in the release notes.

```bibtex
@misc{orchid_literature_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735569},
  url       = {https://doi.org/10.5281/zenodo.23735569},
  note      = {Version 1, machine-extracted}
}

@misc{orchid_hulls_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD)}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735891},
  url       = {https://doi.org/10.5281/zenodo.23735891}
}

@misc{orchid_data_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID data: umbrella record of the ORCHID datasets}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23736065},
  url       = {https://doi.org/10.5281/zenodo.23736065},
  note      = {Version 1, machine-extracted}
}
```

---

Derived data CC BY 4.0 ([licence](https://creativecommons.org/licenses/by/4.0/)): cite ORCHID ([CITATION.cff](https://data.orchid-project.org/CITATION.cff)) and the original sources. Quotes are short excerpts kept so that each value can be checked; they remain under the publishers' copyright and are not relicensed. Source papers, page images and full text are not redistributed. Field reference: [SCHEMA.md](https://data.orchid-project.org/literature/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt). Found an error? The report link of a value (Markdown: its id, ORC-..., in the Location column) opens a pre-filled GitHub issue, https://github.com/orchid-calphad/orchid-data/issues/new?template=report-value-error.yml&record_id=\<id>, carrying only the record id, source and value; [how to contribute](https://orchid-project.org/contribute/).