Source Nernst filament

Sources of infrared emission have included the Globar, which is constructed of silicon carbide. There is also the Nernst filament, which is a mixture of oxides of zirconium, yttrium and erbium. However, a Nernst filament only conducts electricity- at elevated temperatures. ... 

Typical light source Laser Silicon carbide or Nernst Filament ... 

One of the earliest sources was the Nernst filament. This is a mixture of rare earth oxides, primarily of zirconium, made into rods 20-50 mm in length and 1-2.5 mm in diameter. These are fired at 1800°C and have platinum wire connections at both ends. The resultant output at 1800-2000°C is approximately blackbody. However, while relatively cheap to produce these have a very unpredictable life and are very sensitive to environmental factors including draughts. Refractory coated platinum-rhodium wire has been used as a more robust solution but is very expensive. 

Two common sources of infra-red radiation are the Nernst filament, an element of rare earth oxides, mainly zirconium oxide, fused together in a rod between 1 mm and 2 mm diameter, and the Globar, a larger diameter rod of silicon-carbide. Both elements are heated electrically, and at temperatures between 1,200° and 2,000° emit radiation with a maximum between 1 5// and 2 5// rather like a black body radiator. 

Figure 4 Plan view of a Hilger IR spectrometer made in 1918. A constant-deviation Wadsworth optical arrangement with a 60° rock salt prism was employed. The detector was a thermopile and the source a Nernst filament. From Hilger Journal, August 1955. Photograph courtesy Professor N. Sheppard, FRS, and reproduced with permission from Hilger Analytical.

The main sources of infrared radiation used in spectrophotometers are (1) a nichrome wire wound on a ceramic support, (2) the Nernst glower, which is a filament containing zirconium, thorium and cerium oxides held together by a binder, (3) the Globar, a bonded silicon carbide rod. These are heated electrically to temperatures within the range 1200- 2000 °C when they will glow and produce the infrared radiation approximating to that of a black body. 

In the mid-IR several type of sources are used. They are either a lamp filament (Figure 10.13), or a hollow rod, 1-3 mm in diameter and 2 to 4 cm long, made of fused mixtures of zirconium oxide or rare earth oxides (Nernst source) heated by Joule effect by the means of an internal resistor (for example Globar ). These sources are heated to 1500 °C, without a protective shield. They dissipate power of the order of a hundred watts by emitting radiation over a large domain ranging from visible to thermal IR. A maximum is observed for A = 3000/T (A in... 

Source. This usually consists of a filament or rod of some refractory material, heated to a temperature of around 1500 K so as to emit infrared radiation. The Globar is probably the most common source of mid-infrared radiation, consisting of synthetic silicon carbide. This usually has to be water-cooled, however. Filament (Nernst), and nichrome wires are also popular—and may not require water cooling. Water-cooled sources should deliver a higher and more stable output, which is better suited to quantitative applications. 

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