Synthesis
Lanthanum oxide crystallizes as several polymorphs.
To produce hexagonal La2O3, a 0.1 M solution of LaCl3 is sprayed onto a preheated substrate, usually made of metal chalcogenides. The process can be viewed as occurring in two steps – hydrolysis followed by dehydration:
- 2 LaCl3 + 3 H2O → La(OH)3 + 3 HCl
- 2 La(OH)3 → La2O3 + 3 H2O
An alternative route to 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:
- 2 LaCl3+ 3 H2O + 3 NH3 → La(OH)3 + 3 NH4Cl
- LaCl3·3H2O → La2O3
Other routes include:
- 2 La2S3 + 3 CO2 → 2 La2O3 + 3 CS2
- 2 La2(SO4)3 + heat → 2 La2O3 + 6 SO3
Read more about this topic: Lanthanum Oxide
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