chemistry

Lanthanum oxide

Lanthanum oxide is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lanthanum oxide rather than just read about it. In short: Lanthanum(III) oxide, also known as lanthana, chemical formula La2O3, is an inorganic compound containing the rare-earth element lanthanum and oxygen. It is used in some ferroelectric materials, as a component of optical materials, and is a feedstock for certain catalysts, among other uses.

Key takeaways

Lanthanum oxide belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lanthanum oxide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lanthanum oxide from memory before moving on to harder problems.

Reference excerpt

Lanthanum(III) oxide, also known as lanthana, chemical formula La2O3, is an inorganic compound containing the rare-earth element lanthanum and oxygen. It is used in some ferroelectric materials, as a component of optical materials, and is a feedstock for certain catalysts, among other uses.

Properties

Lanthanum oxide is a white solid that is insoluble in water, but dissolves in acidic solutions. La2O3 absorbs moisture from air, converting to lanthanum hydroxide. Lanthanum oxide has p-type semiconducting properties and a band gap of approximately 5.8 eV. Its average room-temperature resistivity is 10 kΩ·cm, which decreases with an increase in temperature. La2O3 has the lowest lattice energy of the rare-earth oxides, with very high dielectric constant ε = 27.

Structure At low temperatures, La2O3 has an A-M2O3 hexagonal crystal structure. The La3+ metal atoms are surrounded by a 7-coordinate group of O2− atoms, the oxygen ions are in an octahedral shape around the metal atom, and there is one oxygen ion above one of the octahedral faces. On the other hand, at high temperatures lanthanum oxide converts to a C-M2O3 cubic crystal structure. The La3+ ion is surrounded by six O2− ions in a hexagonal configuration.

Synthesis Lanthanum oxide can crystallize in at least three polymorphs. Hexagonal La2O3 has been produced by spray pyrolysis of lanthanum chloride:

2 LaCl3 + 3 H2O → La(OH)3 + 3 HCl 2 La(OH)3 → La2O3 + 3 H2O 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:

2 LaCl3 + 3 H2O + 3 NH3 → La(OH)3 + 3 [NH4]Cl Other routes include

2 La2S3 + 3 CO2 → 2 La2O3 + 3 CS2

Reactions Lanthanum oxide is used as an additive to develop certain ferroelectric materials, such as La-doped bismuth titanate (Bi4Ti3O12, "BLT"). Lanthanum oxide is used in optical materials; often the optical glasses are doped with La2O3 to improve the glass' refractive index, chemical durability, and mechanical strength.

3 B2O3 + La2O3 → 2 La(BO2)3 The addition of the La2O3 to the glass melt leads to a higher glass-transition temperature from 658 °C to 679 °C. The addition also leads to a higher density, microhardness, and refractive index of the glass.

Potential applications Lanthanum oxide is most useful as a precursor to other lanthanum compounds. Neither the oxide nor any of the derived materials enjoys substantial commercial value, unlike some of the other lanthanides. Many reports describe efforts toward practical applications of La2O3, as described below. La2O3 forms glasses of high density, refractive index, and hardness. Together with oxides of tungsten, tantalum, and thorium, La2O3 improves the resistance of the glass to attack by alkali. La2O3 is an ingredient in some piezoelectric and thermoelectric materials. La2O3 has been examined for the oxidative coupling of methane.

References

Illustrations

Worked examples

Example 1 — a first encounter with Lanthanum oxide

Start with the simplest possible case. Write down what Lanthanum oxide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lanthanum oxide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lanthanum oxide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lanthanum oxide

In research: Lanthanum oxide appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lanthanum oxide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lanthanum oxide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Inorganic compounds, Lanthanum compounds, Sesquioxides, so understanding it makes those chapters shorter.
In everyday life: Look for Lanthanum oxide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lanthanum oxide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lanthanum oxide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lanthanum oxide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lanthanum oxide in simple terms?

Why does Lanthanum oxide matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lanthanum oxide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lanthanum oxide.