Gadolinium(III) oxide

Gadolinium(III) oxide

Names
Other names gadolinium sesquioxide, gadolinium trioxide
Identifiers
CAS Number	12064-62-9 Y
3D model (JSmol)	Interactive image
ChemSpider	140201 Y
ECHA InfoCard	100.031.861
EC Number	235-060-9
PubChem CID	159427
RTECS number	LW4790000
UNII	5480D0NHLJ Y
CompTox Dashboard (EPA)	DTXSID4051613 DTXSID00912093, DTXSID4051613
InChI InChI=1S/2Gd.3O/q2*+3;3*-2 Y Key: CMIHHWBVHJVIGI-UHFFFAOYSA-N Y InChI=1/2Gd.3O/q2*+3;3*-2 Key: CMIHHWBVHJVIGI-UHFFFAOYAI
SMILES [Gd+3].[Gd+3].[O-2].[O-2].[O-2]
Properties
Chemical formula	Gd2O3
Molar mass	362.50 g/mol
Appearance	white odorless powder
Density	7.07 g/cm3 [1]
Melting point	2,420 °C (4,390 °F; 2,690 K)
Solubility in water	insoluble
Solubility product (Ksp)	1.8×10−23
Solubility	soluble in acid
Magnetic susceptibility (χ)	+53,200·10−6 cm3/mol
Structure
Crystal structure	cubic, cI80, Monoclinic
Space group	Ia-3, No. 206, C2/m, No. 12
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H319, H410
Precautionary statements	P264, P273, P280, P305+P351+P338, P337+P313, P391, P501
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Gadolinium(III) chloride
Other cations	Europium(III) oxide, Terbium(III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Gadolinium(III) oxide (archaically gadolinia) is an inorganic compound with the formula Gd₂O₃. It is one of the most commonly available forms of the rare-earth element gadolinium, derivatives of which are potential contrast agents for magnetic resonance imaging.

Structure

Gadolinium oxide adopts two structures. The cubic (cI80, Ia3), No. 206) structure is similar to that of manganese(III) oxide and heavy trivalent lanthanide sesquioxides. The cubic structure features two types of gadolinium sites, each with a coordination number of 6 but with different coordination geometries. The second polymorph is monoclinic (Pearson symbol mS30, space group C2/m, No. 12).^[2] At room temperature, the cubic structure is more stable. The phase change to the monoclinic structure takes place at 1200 °C. Above 2100 °C to the melting point at 2420 °C, a hexagonal phase dominates.^[3]

Preparation and chemistry

Gadolinium oxide can be formed by thermal decomposition of the hydroxide, nitrate, carbonate, or oxalates.^[4] Gadolinium oxide forms on the surface of gadolinium metal.

Gadolinium oxide is a rather basic oxide, indicated by its ready reaction with carbon dioxide to give carbonates. It dissolves readily in the common mineral acids with the complication that the oxalate, fluoride, sulfate and phosphate are very insoluble in water and may coat the grains of oxide, thereby preventing the complete dissolution.^[5]

Nanoparticles of Gd₂O₃

Several methods are known for the synthesis of gadolinium oxide nanoparticles, mostly based on precipitation of the hydroxide by the reaction of gadolinium ions with hydroxide, followed by thermal dehydration to the oxide. The nanoparticles are always coated with a protective material to avoid the formation of larger polycrystalline aggregates.^[6][7][8]

Nanoparticles of gadolinium oxide is a potential contrast agent for magnetic resonance imaging (MRI). A dextran-coated preparation of 20–40 nm sized gadolinium oxide particles had a relaxivity of 4.8 s⁻¹mM⁻¹ per gadolinium ion at 7.05 T (an unusually high field compared to the clinically used MRI scanners which mostly range from 0.5 to 3 T).^[6] Smaller particles, between 2 and 7 nm, were tested as an MRI agent.^[7][8]

References