Zinc Sulfide Powder
zinc sulfide powder, also known as lithopone, is the most popular white pigment for low-gloss paints, and it is used in many other applications as well. It has better hiding power than Titanium White, Cremnitz White, and many other white pigments and is also much brighter in the dark. It can also be phosphorescent with the addition of copper and is therefore called luminescent zinc sulfide powder.
In nature, ZnS occurs as the black mineral sphalerite and has a density of 0.26 g/cm3 and a melting point of 1020 degC. However, it is produced synthetically in denser forms, such as wurtzite. In a pure form, zinc sulfide is a semiconductor with an electron-filled valence band and an empty conduction band. This large energy gap, or forbidden band, makes the material a semiconductor that can be doped with other elements to increase the concentration of charge carriers. For example, introducing sulphur vacancies turns the white-yellowish ZnS into a brown powder and boosts photocatalytic activity through enhanced light absorption.
With the addition of just a few ppm of suitable activator, ZnS exhibits intense phosphorescence that can be utilized in a range of applications, from cathode ray tubes and X-ray screens to glow in the dark products. When silver is the activator, the resulting color is bright blue with a maximum wavelength at 450 nanometers, while manganese produces an orange-red colour of about 590 nm and copper can be used to produce a long-lasting and familiar greenish glow when illuminated by blue or ultraviolet radiation (ZnS + Cu).
