Phosphor

In a context of chemistry, or when referring to cathode-ray tubes, phosphor refers to any of various compounds of transition metals or of rare earths that exhibits phosphorescence. This is not to be confused with the chemical element phosphorus (symbol P, atomic number of 15) which emits light due to chemiluminescence, not phosphorescence.

CRT phosphors were standardized beginning around World War II and designated by the letter "P" followed by a number. In most early scopes, the standard phosphor was P-2. By the late 1950s, P-31 became dominant. For scopes primarily used with photographic recording, the blue P-11 phosphor was common.

The choice of phosphor for a CRT is based on the intended application of the instrument. The phosphor affects:

trace color
maximum trace brightness
trace width
persistence time
writing rate
resistance to burns

Phosphor

Further reading