Lanthanum oxide is a white solid that is insoluble in water, but dissolves in acidic solutions.

[2] Lanthanum oxide has p-type semiconducting properties and a band gap of approximately 5.8 eV.

La2O3 has the lowest lattice energy of the rare earth oxides, with very high dielectric constant ε = 27.

[4] On the other hand, at high temperatures lanthanum oxide converts to a C-M2O3 cubic crystal structure.

[7] An alternative route to obtaining hexagonal La2O3 involves precipitation of nominal La(OH)3 from aqueous solution using a combination of 2.5% NH3 and the surfactant sodium dodecyl sulfate followed by heating and stirring for 24 hours at 80 °C: Other routes include: Lanthanum oxide is used as an additive to develop certain ferroelectric materials, such as La-doped bismuth titanate (Bi4Ti3O12 - BLT).