Yttrium – Y – Clear white light

Yttrium (Y – Atomic number 39) is another transition metals (like Iron) and was named after the town in Sweden, Ytterby, where the mineral (Ytterbite) in which it was first found was picked up from a quarry. Today Yttrium has a number of uses – as its oxide it is added to glass for camera lenses to improve heat and shock resistance.  We have all starred at it as it was used for making phosphors, such as the red ones in used in televisions (non flat screen), and it is a regular additive to magnesium and aluminium alloys to improve strength  – and probably its most important current use is in the production of white LEDs. So a couple of photography related uses.

White LED from my Christmas lights
White LED from my Christmas lights

I must get a better lens for macros… Yttrium is fairly common – the 28th most abundant element in the earths crust, found in soil and sea water – and strangely found in cabbage (not enough to worry about though).  It is very similar to the lanthanides, its close neighbours in the periodic table, and mostly obtained from the same rare earth minerals.

Camera lens with periodic table reflection
Camera lens with periodic table reflection

The way it is used in white LEDs is interesting, as Cesium doped Yttrium Aluminium Garnet (YAG, Y3Al5O12) – it is a phosphor that emits a yellow light.  As a coating in high brightness blue InGaN diodes this converts some of the blue light to yellow – giving an overall white light.  The spectrum coverage is not perfect though – so even though it appears white the colour rendering isn’t ideal.  It is a fascinating (to me anyway) topic colour rendering – and has always been a challenge for colour photography to get an accurate representation of scenes that match to the way our eyes interpret them.  The colour can be affected very much by the light source – and it the white light doesn’t cover the full visibile spectrum then some colours just won’t look as expected – and this can be further challenged by the viewing conditions.  More over at Wikipedia – and the book The Reproduction of Colour gives lots more detail for those interested.

On final fun fact – and I’m sure gas mantles are something that few will remember – but these were used for propane lanterns (I remember them from caravan holidays) and where often used in the science lab as a demonstration of Geiger counters – as they used to be made with thorium which is radioactive.  Yttrium has replaced thorium now, so I guess science teachers bought up the old stock to keep the demonstrations going!

That finishes my first word – Fe Br U Ar Y – so next up come Tin, Oxygen and Tungsten – one life giver between two metals often connected with war and conflict – and the word is Sn O W.

Camera Lens

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