Full Color Emission in ZnGa₂O₄: Simultaneous Control of the Spherical Morphology, Luminescent, and Electric Properties via Hydrothermal Approach

Abstract

ZnGa2O4 and ZnGa2O4: Mn2+/Eu3+ with uniform nanosphere (diameter about 400 nm) morphology have been synthesized via a facile hydrothermal approach. XRD, Raman spectra, XPS, FT‐IR, SEM, TEM, photoluminescence (PL), and cathodoluminescecne (CL) spectra are used to characterize the resulting samples. The controlled experiments indicate the dosage of trisodium citrate and pH values are responsible for shape determination of the ZnGa2O4 products. The possible fast crystallization–dissolution–recrystallization formation mechanism for these nanospheres is presented. Under UV light and low‐voltage electron beam excitation, ZnGa2O4, ZnGa2O4: Mn2+ and ZnGa2O4: Eu3+ emit bright blue, green, and red luminescence, respectively. Based on density functional theory calculations from first principles, the green and red emission are caused by the Mn 3d and Eu 4f electronic structures, respectively. Besides, the dependence of the CL intensity on the calcination temperature and electrical conductivity of the samples is presented. The ZnGa2O4: Mn2+ nanospheres have a higher CL intensity than that of bulk samples under the same excitation condition. The realization of three primary colors from a single host material suggests that full color display based on ZnGa2O4 nanospheres might be achievable, showing that these materials have potential applications in lighting and display fields.

Crystal-Site Engineering Control for the Reduction of Eu3+ to Eu2+ in CaYAlO4: Structure Refinement and Tunable Emission Properties

“…Generally, the attractive force of the central cations toward the anions can be roughly evaluated by the ionic potential (φ), which can be calculated from φ = Z/r, where Z is the electric charge number of ion, and r is the ion radius (pm). 63,64 It can be obtained that φ(Ca 2+ ) = 0.0169, φ(Y 3+ ) = 0.0279, φ(Si 4+ ) = 0.10, and φ(Al 3+ ) = 0.056. Thus, φ(Ca 2+ ) < φ(Y 3+ ) and φ(Si 4+ ) > φ(Al 3+ ).…”

Controlled Hydrothermal Synthesis and Photoluminescence of Nanocrystalline ZnGa2O4:Cr3+ Monospheres

“…ZnGa 2 O 4 is also known as a type of self-activated phosphors and may emit blue light under short UV or electron beam irradiation, owing to the occurrence of O-Ga charge transfer [1]. As a phosphor host, the Mn 2+ , Eu 3+ , and Cr 3+ activator ions doped into the ZnGa 2 O 4 lattice and residing at the Ga 3+ sites are known to emit bright green, red, and red luminescence under proper excitations, respectively [2]. It is also worth noting that the transition metal ion of Cr 3+ may emit near-infrared persistent luminescence when the chemical composition and lattice defects of ZnGa 2 O 4 are properly manipulated, which allows the material to have potential applications in the optical imaging of vascularization, tumor, and grafted cells [3–5].…”

Luminescence Properties and Decay Kinetics of Mn2+ and Eu3+ Co-Dopant Ions In MgGa2O4 Ceramics

“…Short component changes from 0.31 to 0.14 ms and a long one from 1.98 to 0.77 ms. The decay curves for ZnGa 2 O 4 : 4%Eu 3+ nanospheres and MgGa 2 O 4 : 5%Eu 3+ nanopowders were fitted with a single exponential function with lifetimes 0.472 ms [12] and 0.934 ms [28], respectively. At the same time, the double exponential function was used for the decay profiles in ZnGa 2 O 4 : Eu 3+ nanopowders [14], [15].…”

“…Thus, such materials are often used in display technologies, such as field emission displays, vacuum fluorescent displays etc. [12], [14].…”

“…In order to obtain efficient phosphors, the coexistence of tetrahedral and octahedral cation sites is the key factor for host materials [15]. As far as we know, there are only a few reports of photoluminescence (PL) decay investigations in ZnGa 2 O 4 : Eu 3+ spinel obtained by different methods [12], [14]. Simultaneously, no detailed study has been reported about decay profiles and energy transfer process in MgGa 2 O 4 : Eu 3+ .…”