The improvement of structure and photoluminescence properties of ZnAl2O4: Cr3+ ceramics synthesized by using solvothermal method

ZnAl2O4: Cr3+ nanocrystalswere fabricated by using solvothermalmethod at various temperatures ranging from 160 degrees C to 220 degrees C. The influence of sodium acetate (NaAC) on the structural, photoluminescence and magnetic properties of Cr-doped zinc aluminate ceramics was investigated. The results showed that ZnAl2O4: Cr3+ polycrystals with sphere morphology (about 500 nm) were formed without NaAC in precursors, while after adding NaAC into the precursors, octahedral and hexagonal single crystals of ZnAl2O4: Cr3+ were present. The PL spectra showed a series of sharp emission peaks ranging from 650 nm to 730 nm assigned to spin-forbidden 2E(g)-> 4A(2g) transition of Cr3+ ions in spinel lattices corresponding to the result of EPR. Comparing to the PL spectra of ZnAl2O4: Cr3+ nanocrystals prepared by using sol-gel method, the intensity of R lines (originating from 2E(g)-> 4A(2g) transition of Cr3+ ions in normal spinel lattices) was much larger than that of N lines (originating from2E(g)-> 4A(2g) transition of Cr3+ ions in inverse spinel lattices) for all samples. The EPR and VSM results showed that with grain size increasing, the interaction between Cr-Cr ions became weaker and the ferromagnetism of ZnAl2O4: Cr3+ nanocrystals was enhanced. (C) 2016 Elsevier Ltd. All rights reserved.