Einsteinium(III) oxide

{{chembox

| verifiedrevid =

| Name = Einsteinium(III) oxide

| ImageFile = Kristallstruktur Lanthanoid-C-Typ.png

| ImageSize = 250px

| ImageCaption = __ Es³⁺     __ O²⁻

| ImageFile1 = Es2O3.png

| IUPACName = Einsteinium sesquioxide
Dieinsteinium trioxide
Einsteinium(III) oxide

| Section1 = {{Chembox Identifiers

| CASNo = 37362-94-0

| PubChem = 177221

| PubChem_Comment = charge imbalance

| ChemSpiderID = 154325

| ChemSpiderID_Comment = deprecated

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| Section2 = {{Chembox Properties

| Formula = Es₂O₃

| MolarMass = 554 g/mol (²⁵³Es)

| Appearance = colourless solidArnold F. Holleman, Nils Wiberg: Lehrbuch der Anorganischen Chemie, 102nd Edition, de Gruyter, Berlin 2007, {{ISBN|978-3-11-017770-1}}, p. 1972.

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| Section3 = {{Chembox Structure

| CrystalStruct = Hexagonal

| SpaceGroup = Ia3

| LattConst_a = 370 pm

| LattConst_c = 600 pm{{cite journal |author1=Christine Guéneau |author2=Alain Chartier |author3=Paul Fossati |author4=Laurent Van Brutzel |author5=Philippe Martin |title=Thermodynamic and Thermophysical Properties of the Actinide Oxides |journal=Comprehensive Nuclear Materials 2nd Ed. |date=2020 |volume=7 |pages=111–154 |doi=10.1016/B978-0-12-803581-8.11786-2 |isbn=9780081028667 |s2cid=261051636 |language=en}}

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Einsteinium(III) oxide is an oxide of the synthetic actinide einsteinium which has the molecular formula Es₂O₃. It is a colourless solid.

Three modifications are known. The body-centered cubic form has lattice parameter a = 1076.6 ± 0.6 pm; this allows the ionic radius of the Es³⁺ ion to be calculated as 92.8 pm. The other two forms are monoclinic and hexagonal: the hexagonal form has the lanthanum(III) oxide structure.R. G. Haire, L. Eyring, in: Handbook on the Physics and Chemistry of Rare Earths, Vol. 18 Lanthanoids and Actinides Chemistry (hrsg. von K. A. Gscheidner, Jr., L. Eyring, G. R. Choppin, G. H. Lander), North-Holland, New York 1994, S. 414–505.

Einsteinium(III) oxide can be obtained by annealing einsteinium(III) nitrate in sub-microgram quantities.R. G. Haire, R. D. Baybarz: "Identification and Analysis of Einsteinium Sesquioxide by Electron Diffraction", in: Journal of Inorganic and Nuclear Chemistry, 1973, 35 (2), S. 489–496; {{doi|10.1016/0022-1902(73)80561-5}}.