UVB emitting phosphors based on singly and co-doped Ce³⁺, Gd³⁺ in Li₄ZrF₈ phosphors

Preparation of Li₄ZrF₈:Ce³⁺ and Li₄ZrF₈:Ce³⁺,Gd³⁺ phosphors is described. Data on luminescence characteristics are presented. Hydrothermal route was employed for the synthesis. Li₄ZrF₈ crystallizes in orthorhombic system with Pnma space group. Li atoms are distributed over two sites, both having same coordination of six. Zr is also similarly distributed over two 8 coordinated sites. Li₄ZrF₈:Ce³⁺ emits a broad band UVB light, while the emission of Li₄ZrF₈:Ce³⁺,Gd³⁺ is in form of a narrow line around 311 nm attributed to ⁶P_7/2 → ⁸S_7/2. Both phosphors exhibited a broad excitation spectrum with a peak at 253 nm. The excitation and emission properties are thus adequate enough to obtain UVB light sources using a conventional high pressure mercury vapour lamp or an ultraviolet LED.