Two problems of particle size have been studied in this paper.1. The relationship between the particle size of raw materials ZnS and that of corresponding ACEL phosphors (Zn

Cd)S:Cu.2. The relationship between the particle size of (Zn

Cd)S:Cu and its ACEL luminance.Twelve types of ZnS raw materials with different particle sizes were used in the experiments. The phosphors were prepared at about 850℃ in sulfur atmosphere. The particle size distribution of raw materials and corresponding ACEL phosphors (Zn

Cd)S:Cu were measured by means of sedimentation method.The central particle size

d

50

the logarithmic standard deviation Ina and the sediment mean particle size

d

were calculated. The

d

50

and Ina indicate the centralization position and the dispersive degree of particle size in logarithmic normal distribution

respectively;

q

indicates the position of centre of gravity in particle weight

distribution.Using raw materials with almost same impurity content under the same conditions

we have the following results.