Synthesis and optical properties of ZnAl2O4:Cr3+, Tb3+ powders Trinh Thi Loan, Nguyen Thi Thuy and Nguyen Ngoc Long Eur. Phys. J. Appl. Phys., 64 1 (2013) 10404 Published online: 04 October 2013 DOI: 10.1051/epjap/2013130008