scholarly journals Stoichiometry Effects on the Electrical Conductivity of Lithium-Manganese Spinels

1999 ◽  
Vol 54 (10-11) ◽  
pp. 579-584
Author(s):  
C. B. Azzoni ◽  
M. C. Mozzati ◽  
A. Paleari ◽  
M. Bini ◽  
D. Capsoni ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Transport Process ◽  
Structural Phase ◽  
Charge Carriers ◽  
Lithium Manganese ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Mn Substitution ◽  
Conductivity Behaviour

The electrical conductivity of lithium-manganese spinels is analyzed in samples with different starting Li cationic fraction x. Li-rich spinels, resulting from Li-Mn substitution around the stoi-chiometric value (x= 0.333), show conductivity values higher than that observed in stoichiometric LiMn2O4 . Besides, a conductivity drop, associated with a structural phase transition at about 290 K in LiMn2O4 , progressively disappears by decreasing x, while it is absent in Li-rich samples. Stoi-chiometry effects on the concentration of charge carriers and on the available sites for the hopping transport process are evaluated, as well as the effects due to coexisting insulating phases. The role of the Jahn-Teller effect on the conductivity behaviour of stoichiometric and Li-poor spinels is also considered.

JAHN-TELLER EFFECT OF MOLECULAR COMPLEXES IN LIQUID SOLUTIONS

1994 ◽  
Vol 08 (21n22) ◽  
pp. 1319-1334 ◽  
Author(s):  
J.W. HALLEY ◽  
X.R. WANG
Keyword(s):  
Quantum Coherence ◽  
Berry Phase ◽  
Molecular Complexes ◽  
Liquid Solution ◽  
Teller Effect ◽  
Liquid Systems ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Molecular Dynamics Methods

We review recent work clarifying the sense in which the Jahn-Teller effect can exist in a molecular complex in liquid solution. We review the molecular dynamics methods for modeling such liquid systems using the cupric ion in aqueous solution as an example. We review the experimental evidence for the Jahn-Teller effect in liquids, emphasizing the importance of taking the time scale of the measurement into account. Finally we discuss the role of quantum coherence and the Berry phase in the Jahn-Teller effect.

Cooperative Pseudo Jahn-Teller Effect as Microscopic Mechanism of (OMT)-(LTT) Structural Phase Transition in La2−xBaxCuO4Superconductors

1992 ◽  
Vol 291 ◽  
Author(s):  
Michael D. Kaplan
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Electronic States ◽  
Teller Effect ◽  
Excited Electronic States ◽  
Microscopic Mechanism ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Local Distortions

ABSTRACTA microscopic mechanism for the structural phase transition from the orthorhombic mediate temperature (OMT) phase into the low temperature tetragonal (LTT) one is suggested on the basis of the cooperative pseudo Jahn-Teller effect. The local distortions mixing the ground and the first excited electronic states are ordered antiferrodistortively and are connected in part, with the oxygen octahedra rotations around the [100] axis. The results are in agreement, with the neutron scattering experiments data.

The role of the Jahn-Teller effect in chromium-doped GaAs

1981 ◽  
Vol 14 (8) ◽  
pp. L199-L206 ◽  
Author(s):  
A S Abhvani ◽  
S P Austen ◽  
C A Bates ◽  
J R Fletcher ◽  
P J King ◽  
...  
Keyword(s):  
Teller Effect ◽  
Jahn Teller ◽  
Jahn Teller Effect
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