Synthesis and structures of lithium manganese oxide spinel, LiMn2O4-delta (0 <=delta <= 0.27)

Lithium manganese oxides spinels were synthesized under various synthesis c onditions and their structures were determined by TOF neutron powder diffra ction measurements. Oxygen vacancies exist for the samples synthesized abov e 800 degreesC, and the amount of vacancies was found to be sensitive to th e synthesis conditions. The nearly stoichiometric spinels were synthesized at 750 degreesC in O-2 followed by heating at 470 degreesC, The transition temperatures of the cubic-orthorhombic transitions and the magnetic propert ies varied with the compositions, The stoichiometric spinel showed no cubic -orthorhombic phase transition. (C) 2001 Elsevier Science B.V. All rights r eserved.