Abstract:

A novel red phosphor Zn₆Ga_8-xTiO₂₀:xCr³⁺ was prepared via a high temperature solid-state method. The as-prepared phosphors were examined by means of X-ray diffraction, X-ray fluorescence and transmission electron microscopy. The results showed that the synthesized phosphor had a single mixed spinel structure and Cr³⁺ could be effectively doped into the host Zn₆Ga₈TiO₂₀ by occupation of octahedral sites. It was showed that the excitation spectrum was composed of four bands located at 281, 337, 420 and 555 nm, respectively. The band at 281 nm corresponded to the ⁴A₂-⁴T₁ (4P) transition of Cr³⁺ and that at 337 nm originated from the charge transfer from 2p orbitals of O^2- to the 4s4p orbital of Ga³⁺, while the bands at 420 and 555 nm were related to the transitions of ⁴A₂-⁴T₁ and ⁴A₂-⁴T_2g of Cr³⁺ ions, respectively. The emission spectrum was composed of the zero-phonon lines corresponding to the ²E-⁴A₂ transition of Cr³⁺ (689 nm, R sharp line), the N-line (696 nm) of Cr³⁺ locating at distorted sites, and the phonon-side bands. Therefore, this phosphor can be used as a red phosphor material in white LED.

Key words: Zn6Ga8-xTiO20:xCr, red phosphor, microstructure, emission