Blue tungsten oxide (BTO), a typical tungsten oxide (WO₃₋ₓ), also known as tungsten blue oxide, is a deep blue compound with mixed valence states of tungsten (VI) and tungsten (V). It is an inorganic compound composed of 20 tungsten atoms and 58 oxygen atoms, characterized as an oxygen-deficient/vacancy tungsten oxide. Its English name is Blue Tungsten Oxide (abbreviated as BTO), with a chemical formula of WO₂.₉₀ or W₂₀O₅₈. Note: Depending on calcination conditions, the phase composition of blue tungsten oxide varies, but it is primarily composed of WO₂.₉₀ or ammonium tungsten bronze (ATB) as the main phase.

‌As a typical representative of refractory tungsten products, tungsten heater is deep-processed products made from pure tungsten wire or doped tungsten wire. Known as "tungsten heater" in English, they generally contain over 99.95% tungsten and have diameters ranging from ‌0.2–1.2 mm‌.

Molybdenum sheet is a thin material processed from molybdenum metal, typically ranging from 0.01 to 2 millimeters in thickness. Due to its excellent high-temperature performance, corrosion resistance, and superior mechanical properties, it is widely used in electronics, aerospace, high-temperature furnaces, and chemical industries. Molybdenum sheet can be manufactured in rectangular, circular, or custom shapes, with widths ranging from 10 to 1,000 millimeters and lengths up to 2,000 millimeters or cut to specific requirements.

As a common impurity element in ammonium metatungstate (AMT), sodium primarily affects its physicochemical properties and application performance in the following ways: