Adding impurities to

β

-C

2

S can affect its microstructure

polycrystalline transfer and rate of firing reaction. Being hard dry powder.

β

-C

2

S can not be compressed into pieces

so a vertical experimental arrangement is used. The lifetime spectrum of positrons in

β

-C

2

S powder samples added with Na

2

O and P

2

O

5

is studied. The results show that the component with intermediate lifetime τ

2

(about 470 ps) represents the capture of positrons in Ca

2+

vacancies; the intensity

I

2

of τ

2

decteases with increasing of Na

+

and increases with increasing of P

5+

. The results also show that Na

+

replaces Ca

2+

and creates anion vacancies

but P

5+

creates cation vacancies.