Role of Zinc Ions in Europium Doped Zinc Aluminate Phosphor

Abstract

The demand for efficient, reliable, and high-performance phosphor materials in solid-state lighting and optoelectronic devices has led to significant research into various doped semiconductor materials. One of the most difficult issues in this field is improving the luminous characteristics and structural stability of these materials. This study focuses on the optical and structural characteristics europium (Eu²⁺) doped zinc aluminate (ZnAl₂O₄) doped with different zinc ion concentrations. All the samples was prepared by using urea as the fuel and the combustion method with chemical balance of: 3Zn_(1+x)(NO₃)₂.6H₂O + 6Al(NO₃)₃.9H₂O + 20CH₄N₂O + 1.0 mol% Eu(NO₃)₃ + xZn(NO₃)₂ = 3Zn_(1+x)EuAl₂O₄ + 20CO₂ + 112H₂O + 32N₂. The Eu²⁺ concentration was constant at 1.0 mol%, while zinc ions values varied from 1.0 mol% to 1.8 mol%. Combustion was carried out with temperature of 600 ºC, phosphors were converted from liquid to fine white nanoparticles. All the samples were characterized using the X-ray diffraction (XRD) method, photoluminescence (PL) spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy. The XRD patterns showed consistent peak positions and sharp diffraction peaks, indicating high crystallinity and phase purity of the synthesized samples. Photoluminescence analysis revealed that the highest emission intensity occurred at a zinc concentration of 1.2 mol% after exited with 350 nm. The CIE 1931 analysis indicated that europium-doped zinc aluminate emitted warm yellowish-red light with correlated color temperature (CCT) values ranging from 2145 K to 2702 K. Furthermore, UV-Vis spectroscopy analysis showed major UV absorption around 200 nm for all samples, gradually decreasing towards the visible region. The sample with 1.8 mol% of zinc concentration exhibited the highest UV absorbance, while pure ZnAl₂O₄ displayed the lowest.