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

Abstract ZnAl2O4:Cr3 + nanocrystals were fabricated by using solvothermal method at various temperatures ranging from 160 °C to 220 °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 2Eg → 4A2g 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 2Eg → 4A2g transition of Cr3 + ions in normal spinel lattices) was much larger than that of N lines (originating from 2Eg → 4A2g 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.