chemistry

Indium(III) oxide

Indium(III) 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 Indium(III) oxide rather than just read about it. In short: Indium(III) oxide (In2O3) is a chemical compound, an amphoteric oxide of indium. Physical properties Crystal structure Amorphous indium oxide is insoluble in water but soluble in acids, whereas crystalline indium oxide is insoluble in both water and acids.

Key takeaways

Indium(III) 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 Indium(III) oxide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Indium(III) oxide from memory before moving on to harder problems.

Reference excerpt

Indium(III) oxide (In2O3) is a chemical compound, an amphoteric oxide of indium.

Physical properties

Crystal structure Amorphous indium oxide is insoluble in water but soluble in acids, whereas crystalline indium oxide is insoluble in both water and acids. The crystalline form exists in two phases, the cubic (bixbyite type) and rhombohedral (corundum type). Both phases have a band gap of about 3 eV. The parameters of the cubic phase are listed in the infobox. The rhombohedral phase is produced at high temperatures and pressures or when using non-equilibrium growth methods. It has a space group R3c No. 167, Pearson symbol hR30, a = 0.5487 nm, b = 0.5487 nm, c = 1.4510 nm, Z = 6 and calculated density 7.31 g/cm3.

Conductivity and magnetism Thin films of chromium-doped indium oxide (In2−xCrxO3) are a magnetic semiconductor displaying high-temperature ferromagnetism, single-phase crystal structure, and semiconductor behavior with high concentration of charge carriers. It has possible applications in spintronics as a material for spin injectors. Thin polycrystalline films of indium oxide doped with Zn2+ are highly conductive (conductivity ~105 S/m) and even superconductive at liquid helium temperatures. The superconducting transition temperature Tc depends on the doping and film structure and is below 3.3 K.

Synthesis Bulk samples can be prepared by heating indium(III) hydroxide or the nitrate, carbonate or sulfate. Thin films of indium oxide can be prepared by sputtering of indium targets in an argon/oxygen atmosphere. They can be used as diffusion barriers ("barrier metals") in semiconductors, e.g. to inhibit diffusion between aluminium and silicon. Monocrystalline nanowires can be synthesized from indium oxide by laser ablation, allowing precise diameter control down to 10 nm. Field effect transistors were fabricated from those. Indium oxide nanowires can serve as sensitive and specific redox protein sensors. The sol–gel method is another way to prepare nanowires. Indium oxide can serve as a semiconductor material, forming heterojunctions with p-InP, n-GaAs, n-Si, and other materials. A layer of indium oxide on a silicon substrate can be deposited from an indium trichloride solution, a method useful for manufacture of solar cells.

Reactions When heated to 700 °C, indium(III) oxide forms In2O, (called indium(I) oxide or indium suboxide), at 2000 °C it decomposes. It is soluble in acids but not in alkali. With ammonia at high temperature indium nitride is formed:

In2O3 + 2 NH3 → 2 InN + 3 H2O With K2O and indium metal the compound K5InO4 containing tetrahedral InO45− ions was prepared. Reacting with a range of metal trioxides produces perovskites for example:

In2O3 + Cr2O3 → 2InCrO3

Applications Indium oxide is used in some types of batteries, thin film infrared reflectors transparent for visible light (hot mirrors), some optical coatings, and some antistatic coatings. In combination with tin dioxide, indium oxide forms indium tin oxide (also called tin doped indium oxide or ITO), a material used for transparent conductive coatings. In semiconductors, indium oxide can be used as an n-type semiconductor used as a resistive element in integrated circuits. In histology, indium oxide is used as a part of some stain formulations.

See also Indium Indium tin oxide Magnetic semiconductor

References

Illustrations

Worked examples

Example 1 — a first encounter with Indium(III) oxide

Start with the simplest possible case. Write down what Indium(III) 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 Indium(III) 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 Indium(III) 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 Indium(III) oxide

In research: Indium(III) 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 Indium(III) 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: Indium(III) oxide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Indium compounds, Semiconductor materials, Sesquioxides, so understanding it makes those chapters shorter.
In everyday life: Look for Indium(III) 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 Indium(III) oxide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Indium(III) 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 Indium(III) oxide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Indium(III) oxide in simple terms?

Indium(III) oxide (In2O3) is a chemical compound, an amphoteric oxide of indium. Physical properties Crystal structure Amorphous indium oxide is insoluble in water but soluble in acids, whereas crystalline indium oxide is insoluble in both water and acids.

Why does Indium(III) 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 Indium(III) 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 Indium(III) oxide.