Holmium is a silver-white metal, soft and ductile; melting point is 1474°C, boiling point is 2695°C, and density is 8.7947g/cm³. Holmium is stable in dry air and oxidizes quickly at high temperatures; holmium oxide is the most paramagnetic substance known. Compounds of holmium can be used as additives for new ferromagnetic materials; holmium iodide is used to make metal halide lamps - holmium lamps.
Stability
Stable in dry air at room temperature, easily oxidized in humid air and high temperature. Avoid contact with air, oxides, acids, halogens, moist moisture, and release flammable gases when in contact with water; soluble in inorganic acids. Stable in dry air at room temperature, but oxidizes rapidly in moist air and above room temperature. Chemically active. Slowly decompose water. Can be combined with almost all non-metallic elements. Exist in silicon beryllium yttrium, monazite and other rare earth minerals. Used to make magnetic alloy materials.
Chemical properties
Like dysprosium, it is a metal that absorbs neutrons produced by nuclear fission.
In a nuclear reactor, on the one hand, it burns continuously, and on the other hand, it controls the speed of the chain reaction.

Application field
(1) It is used as an additive for metal halide lamps. Metal halide lamps are a kind of gas discharge lamps, which are developed on the basis of high-pressure mercury lamps. They are characterized by filling the bulb with various rare earth halides. Rare earth iodides are mainly used, which emit different spectral light colors during gas discharge. The working substance used in the holmium lamp is holmium iodide, which can obtain a higher concentration of metal atoms in the arc region, thereby greatly improving the radiation efficiency.
(2), holmium can be used as an additive of yttrium iron or yttrium aluminum garnet;
(3) The holmium-doped yttrium aluminum garnet (Ho:YAG) can emit 2μm laser, and the absorption rate of human tissue to 2μm laser is high, which is almost 3 orders of magnitude higher than that of Hd:YAG. Therefore, when the Ho:YAG laser is used for medical surgery, it can not only improve the efficiency and precision of the surgery, but also reduce the thermal damage area to a smaller size. The free beam produced by holmium crystals can remove fat without generating excessive heat, thereby reducing thermal damage to healthy tissue. It is reported that the United States uses holmium lasers to treat glaucoma, which can reduce the pain of surgery for patients. The level of China's 2μm laser crystal has reached the international level, and this laser crystal should be vigorously developed and produced.
(4) In the magnetostrictive alloy Terfenol-D, a small amount of holmium can also be added to reduce the external field required for the saturation magnetization of the alloy.
(5) In addition, holmium-doped fiber can be used to make fiber lasers, fiber amplifiers, fiber sensors and other optical communication devices, which will play a more important role in today's rapid fiber communication.