Preliminary data of the biodiversity in the area VNU Journal of Science Mathematics – Physics, Vol 34, No 1 (2018) 1 7 1 Synthesis and Optical Properties of ZnAl2O4/Al2O3 Cr 3+ Composite Materials Trinh Thi Loan * , Nguyen Ngoc Long Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam Received 16 January 2018 Revised 02 February 2018; Accepted 15 March 2018 Abstract Zinc aluminate alumina (ZnAl2O4/Al2O3) systems doped with Cr 3+ different concentrations were[.]