Jahn–Teller transition in Al3+ doped LiMn2O4 spinel

✍ Scribed by Doretta Capsoni; Marcella Bini; Gaetano Chiodelli; Vincenzo Massarotti; Piercarlo Mustarelli; Laura Linati; Maria Cristina Mozzati; Carlo B. Azzoni

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 256 KB
• Volume: 126
• Category: Article
• ISSN: 0038-1098
• DOI: 10.1016/s0038-1098(03)00129-7

✦ Synopsis

Al-doped lithium manganese spinels, with starting composition Li 1.02 Al x Mn 1.982x O 4 ð0:00 , x # 0:06Þ; are investigated to determine the influence of the Al 3þ doping on the Jahn -Teller (J-T) cooperative transition temperature T J -T : X-ray powder diffraction (XRPD), nuclear magnetic resonance, electron paramagnetic resonance, conductivity and magnetic susceptibility data are put into relation with the tetrahedral and octahedral occupancy fraction of the spinel sites and with the homogeneous distribution of the Al 3þ ions in the spinel phase. It is observed that Al 3þ may distribute between the two cationic sublattices. The J -T distortion, associated with a drop of conductivity near room temperature in the undoped sample, is shifted towards lower temperature by very low substitution. However, for x . 0:04 T J -T it increases with increasing x; as clearly evidenced in low temperature XRPD observations. A charge distribution model in the cationic sublattice, for Al substitution, is proposed to explain this peculiar behavior.