23.12/2022
Merry Christmas and Happy New Year 2023!
27.06/2022
POLEMA’s QMS confirmed its compliance with ISO 9001:20015
POLEMA JSC confirmed the compliance of the current QMS with the requirements of ISO 9001:2015.
03.06/2011
Progressive materials for multi-functional vacuum coatings
Application fields of materials for multi-functional vacuum coatings, characteristics of sputtering targets and evaporable sources used for technologies of physical deposition of hardening, protective, decorative and light-reflecting coatings, resistive, switching and transparent electro conductive films.
24.05/2011
Molybdenum and tungsten products for production of leucosapphires
POLEMA JSC is the leading global manufacturer of chromium, molybdenum, tungsten products, metal powders and composite materials.
Tungsten crucibles
Use
Tungsten crucibles, thanks to their resistance to certain molten metals and metal oxides, have found wide use in technologies for growing single crystals from molten corundum, as well as in electronics and technologies for thermal vaporization - deposition of various substances.
Chemical composition
Grade | W, % minimum | Impurities, ppm, maximum | ||||||||
Crucible W-PM | 99.0 | Fe | Ni | Al | Mo | Si | K | Na | Ca | As |
80 | 50 | 10 | 400 | 30 | 200 | 150 | 50 | 50 |
Upon agreement with the client, crucibles can be prepared with additions of molybdenum of up to 0.9%, and with other requirements regarding the material's chemical composition.
Shapes, dimensions and surface condition of W-PM crucibles
Crucibles are made in accordance with drawings. The shape and dimensions are agreed upon with the client. The surface roughness of tooled crucibles does not exceed Rz 6.3.
Sample dimensions of sintered tungsten crucibles W-PM, diameter Ø x height, mm:
- Ø130x150;
- Ø200x240;
- Ø240x300;
- Ø250x350-400;
- Ø330x350;
- Ø330x450;
- Ø338x460;
- Ø350x460;
- Ø350x495;
- Ø380x530.
Modestly sized crucibles made form tungsten - for example, with diameters of 40-50 mm - can be produced based on drawings agreed to with the client.
Crucible density:
- Sintered crucibles W-PM – at least 17.8 g/cm³;
Advantages:
- the products' fairly high chemical purity, which ensures sapphire single crystals free from impurities;
- a fairly wide selection of standard product sizes, to fulfill consumers' order quickly;
- the ability to develop products with new sizes based on the client's individual needs.
Recommendations on using and storing crucibles.
Before use, it is recommended that the consumer anneal (de-gas) crucibles in a vacuum without batch charging.
In a furnace, the annealment process should be supported with a vacuum at P < 10-4 mm Hg
Heating and cooling technique:
- raise temperature (T) to 1000 ºC over a period of 3 hrs;
- hold at T=1000 ºC for at least 1 hr;
- raise to T=1400-1500 ºC for at least 1 hr;
- hold at T=1400-1500 ºC for at least 1 hr;
- raise to T=2000-2200 ºC for at least 1 hr;
- hold at T=2000-2200 ºC for at least 1 hr;
- cool crucibles in furnace.
When preparing a crucible for work, the consumer should not allow a sharp rise or fall in temperature or shorten the recommended time periods for holding temperatures.
While preparing the crucible for work and during operation, it should not be subjected to shocks.
The manufacturer packs crucibles into wooden packaging (crates) with crash pads. During transport and storage, the crucibles are not submitted to sharp jolts or shocks. They are stored in the manufacturer's packaging in closed, dry fnd heated warehouses.