Holmium oxide, also known as holmium trioxide, Ho2O3, is a compound of the rare earth element holmium and oxygen, and dysprosium oxide is one of the strongest known paramagnetic substances. Holmium oxide is a component of the erbium oxide mineral. In its natural state, holmium oxide often coexists with the trivalent oxides of the lanthanide and requires special methods to separate it. Holmium oxide can be used to prepare glass of special color. The visible absorption spectrum of glass and solutions containing holmium oxide has a series of sharp peaks and has traditionally been used as the calibration standard for spectrometers.

Chinese name: holmium oxide, holmium trioxide

English name: holmiumoxide

Chemical formula: Ho2O3

Relative molecular mass: 377.86

CAS: 39455-61-3

Physical properties: density: 8.36g/cm3, melting point: 2367℃

Chemical properties: holmium oxide reacts with hydrochloric acid or ammonium chloride to produce holmium chloride: Ho2O3+6NH4Cl→2HoCl3+6NH3+3H2O

Solubility: insoluble in water, soluble in acids.

Appearance and properties: light yellow crystalline powder. According to the light condition, the holmium oxide has quite significant color change. Light yellow under sunlight and strong orange under tricolour light source are almost indistinguishable from erbium oxide under the same light, which is related to its sharp phosphorescent emission band. Holmium oxide has a band gap up to 5.3eV wide and, therefore, should be colorless. The yellow color of holmium oxide is caused by a large number of lattice defects (such as oxygen vacancy) and the internal conversion of Ho3+.