Rare Earth Doped Tungsten Electrode History

Pure tungsten electrode is the earliest used electrode material. Mainly because tungsten has high melting point, low vapor pressure and other properties. However, pure tungsten work function is too high and at high temperature recrystallization will occur to form equiaxed crystal structure, so that the material becomes brittle and fracture. In order to improving the recrystallization and reducing the work function temperature of the tungsten electrode, after research people developed a series of rare earth doped tungsten electrodes.

Rare earth doped tungsten electrode is based on tungsten doped with some refractory oxide as the active material, lowering the work function of tungsten. Common rare earth doped tungsten electrodes are thorium tungsten electrode, cerium tungsten electrode, lanthanum tungsten electrode and zirconium tungsten electrode. Thorium tungsten electrode was invented in 1913. It has good performance, but radioactive, so long-term use would endanger human health and cause environmental pollution. Comparing with thorium tungsten electrode, cerium tungsten electrode and lanthanum tungsten electrode has a relatively better performance, and no radioactive, having broad application prospects.

Rare earth doped tungsten electrode began at former Soviet Union. The Soviet Union had reports of rare earth doped tungsten electrode before the 1960s. China, in 1973, had successful developed and used cerium tungsten electrode.

The late 1980s, Japanese researchers achieved some progress in new electrode material, developed a series of rare earth tungsten electrodes, including tungsten electrodes doped with single oxide, tungsten electrodes doped with two oxide and tungsten electrodes doped with three oxide. In tungsten electrodes doped with single oxide, lanthanum tungsten electrode overall performance is better, followed by yttrium tungsten electrode and cerium tungsten electrode. In tungsten electrodes doped with two oxides, producing it with following proportioning will have better property, La₂O₃: CeO₂ = 1: 1, La₂O₃: Y₂O₃ = 1: 3, CeO₂: Y₂O₃ = 1: 3. Tungsten electrodes doped with there oxides (La₂O₃: CeO₂: Y₂O₃ = 1: 1: 3) have low work function, and low operating temperatures.