Nernst glower
Definition and meaning of Nernst glower in chemistry.
A Nernst glower is an electrically heated ceramic rod made from a sintered mixture of zirconium, yttrium, and erbium oxides that emits infrared radiation, historically used as a radiation source in infrared spectroscopy.
In more detail
The device consists of a ceramic rod fabricated from a sintered oxide mixture, typically zirconium oxide, yttrium oxide, and erbium oxide in an approximate 90:7:3 ratio by weight, that must first be preheated to approximately 1000°C or higher, at which point the material becomes conductive and allows electric current to flow. Once heated, the incandescent ceramic emits continuous broadband infrared radiation spanning the mid- and far-infrared regions. The Nernst glower was invented by German physical chemist Walther Nernst and served as a dominant infrared source for analytical spectroscopy instruments during the early-to-mid 20th century. It has been largely replaced by more stable modern alternatives such as globars and quantum cascade lasers, which offer superior stability, longer operational lifetime, and greater ease of use.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Material composition | Sintered ZrO2, Y2O3, and Er2O3 (~90:7:3 by weight) |
| Operating principle | Thermal infrared emission from electrically heated ceramic rod |
| Historical role | Primary infrared source for spectroscopy instruments, early-to-mid 20th century |
A typical mid-infrared spectrometer from the 1950s would employ a Nernst glower as the broadband thermal radiation source, with the emitted infrared light passing through a chemical sample and then analyzed by a detector to measure the sample's absorption spectrum.
Frequently asked questions
Why must a Nernst glower be preheated?
The cold zirconium/yttrium/erbium oxide ceramic has extremely high electrical resistance and will not conduct electric current at room temperature. Preheating to approximately 1000°C reduces the material's resistance dramatically, allowing current to flow and produce thermal infrared radiation.
Why have Nernst glowers become less common in modern spectroscopy?
Modern infrared sources like globars and laser-based systems provide superior stability, longer lifespan, lower maintenance requirements, and greater ease of operation compared to the Nernst glower.