Defect aggregation in anion-excess fluorites. Dopant monomers and dimers

Electrical Study of Pr3+ Ion Environment in Ca1?xPrxF2+x Thin Films

“…It is remarkable to note that the activation energy found here is in excellent agreement with the theoretical value of the energy change associated with such an arrangement in nn centers, found by Corish et al [35]. Moreover, this value (0.64 AE 0.02) eV is close to that obtained for the same defects in Ca 1Àx Er x F 2x thin films (0.68 eV) [32].…”

“…Their average activation energy E dl (0.64 AE 0.02) eV and t 0l % (8 AE 1) Â 10 À13 s are independent of x varying from 0.001 to 0.05. The optical [7,10,11] and theoretical [35] results indicate that, in CaF 2 , among many possible Pr 3 ±F À i arrangements, which behave like dipoles, the nn pairs predominate. Consequently, the Dl observed polarization must be essentially due to limited charge transfers into these defects.…”

Quantum Mechanical Study of the Lattice Distortions Induced by Aliovalent Pb2+ Impurities in Alkali Halides

“…When the impurity is aliovalent the problem of charge compensation emerges. Usually charge compensation is achieved by the creation of a cationic vacancy in the host lattice [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. That vacancy can be in nearest-neighbor (NN) or next-nearest-neighbor (NNN) positions [23], and it induces a static crystal field of symmetry lower than cubic.…”

Light scattering and computational simulations of the superionic behaviour of CaF 2 doped with lanthanide ions

“…On the other hand, the enhanced ion mobility model has been invoked in which the presence of defect clusters and the resultant perturbed lattice result in low energy routes for fluorine interstitial migration [11]. It has also been proposed that interstitial defects are released from the extrinsic clusters leading to the reductions of T c [12]. Recent molecular dynamics (MD) simulations associate the enhanced conductivity with extrinsic fluorine interstitial motion [13].…”