ZnGa₂O₄ and ZnGa₂O₄:Mn²⁺ for potential use in vacuum fluorescent displays

Abstract

Zinc gallate and Mn²⁺-activated zinc gallate were identified as potential low-voltage cathodoluminescent phosphors for use in vacuum fluorescent displays. The stability of these oxide phosphors in high-vacuum and absence of corrosive gas emission under electron bombardment, offer advantages over commonly used sulfide phosphors.

A low-voltage cathodoluminescence spectrophotometer was developed for phosphor characterization. Sample brightness was measured as a function of anode voltage (10-300 VDC). The effects of activator concentration, phosphor layer thickness, deposition process, and internal pressure were examined. From photoluminescence measurements, absorption and emission centers were identified, the role of composition in the luminescence process explained, and host-to-activator, non-radiative energy transfer identified for ZnGa₂0₄:Mn²⁺.

Samples of the general composition Zn_1-xMn_xGa₂O₄, with x ranging from 0 to 0.03, were synthesized by solid-state reaction techniques using oxide precursors fired in air, followed by reduction firing in 98%N₂, 2%H₂. The phase-pure ZnGa₂O₄ spinel structure of all the compositions was characterized by X-ray diffraction.