Page 51 - Curriculum Visions Dynamic Book

See Vol. 6: Dyes, paints, and adhesives for more on dyes and pigments.
times more efficient in their use of energy than any other kind of bulb. That is why they are found so widely despite their colour.
Ceramics as pigments
Ceramics have long been used as pigments in paints and glazes. That is, fine powdered ceramics have been used as the colouring agent.
Their value is that some ceramics (particularly those derived from the rare earths and transition metals) absorb all kinds of light except over a very narrow band. They reflect on this band, producing colour.
Cobalt aluminate and cobalt silicate are blue; tin-vanadium oxide and zirconium-vanadium oxide are yellow, for instance.
Because they are almost inert (unreactive) and only change at very high temperatures, these powdered
(Above) Paints contain ceramics as pigments.
(Above) Phosphors showing on the screen of a television tube.
ceramics can be used at high temperatures, such as when firing a pot in a kiln.
Ceramics phosphors
However, ceramics can also be used to give out light, not just reflect it. Materials that give out light are called phosphors. Phosphors are found in fluorescent lights and as the coloured dots on a television screen.
Phosphors are ceramics that emit light when they are activated by heat, electricity, X-rays, or light. The light they send out is in a very narrow band, and so they produce very precisely coloured light. Phosphors
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