The present invention relates to a plasma display device apt to increase
luminance of a phosphor layer and prevent degradation of a discharge
characteristic, and to a phosphor used for the device. This plasma
display device has a green phosphor having a crystal structure of
Zn.sub.2SiO.sub.4:Mn, and a monovalent oxide is substituted for part of
the green phosphor. The monovalent oxide is one or more of lithium oxide
(Li.sub.2O), sodium oxide (Na.sub.2O), potassium oxide (K.sub.2O), cesium
oxide (Cs.sub.2O), rubidium oxide (Rb.sub.2O), copper oxide (Cu.sub.2O),
and silver oxide (Ag.sub.2O). This structure allows reduction of oxygen
defects occurring in the green phosphor, suppression of the luminance
decrease of the green phosphor, and improvement of a discharge
characteristic.