Due to the support of antiqueradios.com forum users in the thread https://antiqueradios.com/forums/viewtopic.php?f=3&t=407269, I have completed the trial synthesis of the phosphor ZnS: Ag, ZnS, CdS: Ag (P4 type) for black and white cathode ray tubes . I synthesized the yellow component, the blue component was ready, so I didn't do it.
Perhaps I will experimentally make some blue phosphor as well.
I thought that this information might be useful to someone in the future, if the phosphor P4 was no longer available.