混合尖晶石型Zn6Ga8TiO20:Cr3+荧光粉的合成、结构表征与发光性能

采用高温固相法合成新型红色荧光粉Zn₆Ga_8-xTiO₂₀:xCr³⁺。用XRD、XRF和TEM对样品的成分和晶体结构进行表征, 发现所合成的荧光粉为单一的混合尖晶石结构, Cr³⁺能有效地掺杂进入基质Zn₆Ga₈TiO₂₀中, 并占据八面体格位。荧光光谱分析表明, 激发谱由四个峰组成, 峰值分别为281、337、420和555 nm, 其中281 nm对应Cr³⁺离子的⁴A₂→⁴T₁(4P)跃迁, 337 nm来自O^2-的2p轨道电子向Ga³⁺的4s4p轨道迁移跃迁, 420和555 nm分别对应Cr³⁺离子的⁴A₂→⁴T₁和⁴A₂→⁴T_2g的跃迁。发射光谱是由²E→⁴A₂的跃迁辐射零声子线(689 nm, R锐线)、处于畸变的环境中Cr³⁺发射的N线(696 nm)以及由晶格振动导致的声子伴随发射峰组成。这种荧光粉是一种可能应用在白光LED上的红色荧光粉。

Microstructure Characterization and Luminescent Property of Mixed Spinel Zn6Ga8TiO20:Cr3+ Phosphors

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.