Metal oxides and hydroxides

Copper ferrite

Copper ferrite (CuFe₂O₄, also called cuprospinel) is a magnetic spinel ceramic of copper, iron, and oxygen, studied for soft magnetic components and as a photocatalyst in water treatment.

Dicalcium phosphate

Dicalcium phosphate, or dibasic calcium phosphate, is the calcium phosphate salt CaHPO4, used as the food additive E 341 (ii), a feed phosphate, and a bone-repair ceramic.

Friedel's salt, also called calcium chloro-aluminate, is a calcium chloroaluminate hydrate (Ca₂Al(OH)₆Cl·2H₂O) forming in Portland cement, and its chloride binding retards corrosion of steel reinforcement.

Gadolinium(III) oxide

Gadolinium(III) oxide (Gd₂O₃), also called gadolinia or gadolinium sesquioxide, is the white, water-insoluble oxide of the rare-earth metal gadolinium, used to make phosphors, MRI contrast agents, and neutron-shielding materials.

Germanium dioxide

Germanium dioxide (GeO₂), also called germania, is the stable oxide of germanium, a white water-soluble solid used in optical fiber manufacture, as a PET catalyst, and as a germanium feedstock.

Goethite

Goethite is an iron oxyhydroxide mineral named for Johann Wolfgang von Goethe, forming as a weathering product of iron-bearing minerals and serving as ore and yellow ochre pigment.

Green rust

Green rust is a family of mixed Fe(II)–Fe(III) layered double hydroxide compounds, named in 1959, that form during iron corrosion and reduce contaminants such as nitrate and Cr(VI).

Hafnium(IV) oxide

Hafnium(IV) oxide, also known as hafnia (HfO₂), is a white, chemically stable oxide of hafnium. It replaced silicon dioxide as the gate insulator in Intel's 45 nm chips in 2007 and underlies ferroelectric memory.

High-entropy oxides

High-entropy oxides are multicomponent oxide ceramics, typically with five or more cations in near-equiatomic ratios, known for intrinsically low thermal conductivity and use in thermal barrier coatings.

Hydrotalcite

Hydrotalcite is a carbonate-bearing magnesium–aluminum hydroxide mineral, first described in 1842 from the Urals, and the archetype of the layered double hydroxides, or anionic clays.

Oct 21, 2026

Hydrotalcite anhydrous

Hydrotalcite anhydrous is the water-free form of the magnesium-aluminum hydroxycarbonate mineral Mg6Al2(OH)16CO3·4H2O, a layered double hydroxide used as the antacid Talcid for heartburn, gastritis, and acid-peptic disease.

Hydroxide

Hydroxide, also called the hydroxide anion or OH⁻ ion, is the diatomic anion that is the conjugate base of water; its compounds include sodium hydroxide, hydroxide minerals, and layered double hydroxides.

Iridate

An iridate is a compound oxide of iridium, studied in condensed matter physics for 5d perovskites whose bandwidth, Coulomb interaction, and spin-orbit coupling produce unusual insulating states.

Iridium tetroxide

Iridium tetroxide, [IrO4]+, is a gas-phase iridium oxide cation in which iridium reaches oxidation state IX, the highest experimentally identified for any element, reported in 2014.

Iridium(IV) oxide

Iridium(IV) oxide (IrO2, iridium dioxide) is the most common oxide of iridium, a blue-black crystalline solid with the rutile structure and metallic conductivity, serving as the benchmark anode catalyst for acidic water electrolysis.

Iron(III) hydroxide

Iron(III) hydroxide, also called ferric hydroxide, is the hydroxide of trivalent iron with formula Fe(OH)₃, best known as the brown precipitate from iron(III) salts and base.

Iron(III) oxide-hydroxide

Iron(III) oxide-hydroxide (FeOOH), also called yellow iron oxide, is a family of ferric oxyhydroxide compounds occurring as polymorphs including goethite, the main yellow pigment in ochre.

La2PrNi2O7

La2PrNi2O7 is a praseodymium-doped bilayer nickelate that becomes a bulk high-temperature superconductor under pressure above about 11 GPa, with a record onset temperature of 82.5 K.

Layered double hydroxides

Layered double hydroxides (LDHs), also called anionic clays or hydrotalcite-like compounds, are ionic lamellar solids with positively charged brucite-like metal hydroxide layers separated by exchangeable interlayer anions and water.

Layered sodium cobaltate

Layered sodium cobaltate (NaxCoO2) is a layered cobalt oxide whose sodium content controls its properties; it shows a large thermoelectric power, and its hydrate superconducts near 5 K.

Lithium hydroxide

Lithium hydroxide (LiOH) is a white hygroscopic solid, the strongest alkali-metal hydroxide in commercial use, serving as a carbon dioxide scrubber in spacecraft and a battery cathode precursor.

Lithium oxide

Lithium oxide (Li₂O), also called dilithium monoxide, is a white ionic solid known as a candidate tritium breeding ceramic for fusion reactor blankets, studied since the 1980s.

Lye

Lye, also known as alkaline liquor, is the common name for strongly alkaline hydroxide compounds, chiefly sodium hydroxide and potassium hydroxide, both corrosive white solids best known for making soap.

Magnesium ferrite

Magnesium ferrite (MgFe₂O₄), also called magnesioferrite in its mineral form, is a magnetic iron oxide with the cubic spinel structure, a soft magnetic n-type semiconductor used in photocatalysis and gas sensing.

Magnesium hydroxide

Magnesium hydroxide is an inorganic compound, a white solid of low water solubility occurring as the mineral brucite and best known as the antacid and laxative milk of magnesia.

Magnesium oxide

Magnesium oxide (MgO), also called magnesia, is a white inorganic compound of magnesium and oxygen that occurs as the mineral periclase and is used mainly as a refractory in furnace linings.

Manganese oxide nanoparticles

Manganese oxide nanoparticles, also called MnOₓ NPs, are nanoscale particles of manganese oxides including MnO, MnO₂, and Mn₃O₄, used in energy storage, catalysis, and biomedical imaging.

Manganese-oxo cubane

A manganese-oxo cubane is a molecular cluster with manganese ions and oxide bridges alternating at the corners of a cube, best known as a model for photosynthesis's oxygen-evolving complex.

Manganese-oxo cubane water oxidation catalysts

Manganese-oxo cubane water oxidation catalysts are Mn₄O₄-type molecular clusters, bioinspired by the oxygen-evolving complex of photosystem II, that oxidize water to oxygen; the Dismukes cubane exceeds 1000 catalytic turnovers on Nafion electrodes.