Dielectric polarizability of ions and the corresponding effective number of electrons

Abstract

In a previous paper it was shown that in-crystal ion polarizabilities derived from low-frequency precision measurements of the dielectric constants of single-crystal oxides can be given a quantitative interpretation using a quantum mechanically based result for a single, completely filled, electron subshell. In this paper, by exploiting the fact that the radii of related subshells differ only slightly, we propose an equation amended to include the possibility of contributions from incomplete or several subshells. Using the new result, effective electron numbers are derived for all the ions for which experimental polarizabilities have recently been published. It is shown that there is generally a good correspondence between these numbers and the known electronic configurations of the ions concerned. The new calculations show that the concept of a polarizability determined by the contribution of a single electron subshell is certainly valid with ions corresponding to elements of low atomic number, but that in the case of transition and rare earth ions there is probably more than one contributing electron subshell.

The importance of network structure in high-k dielectrics: LaAlO3, Pr2O3, and Ta2O5

“…͑3͒ together with the measured refractive index of 2.1 we obtain ␣ opt ͑Ta 2 O 5 ͒ = 11.3ϫ 10 −24 cm 3 , this discrepancy is in the same sense and of similar magnitude ͑almost a factor of 2͒ as that observed when treating the case of RE 2 O 3 compounds above. It would appear that the calculated ionic polarizabilities 24 are almost a factor of 2 too large.…”

“…The observed monotonic decrease of the effective polarizability across the RE series is apparently, however, supported both on the basis of the optical and low-frequency measurements. Calculations of ␣ opt may be made using the published individual ionic components 24 ͑␣ RE 3+ and ␣ O 2−͒ for the closed-shell configurations of the individual ions. Though the absolute magnitude is in disagreement with experiment, again the general trend of a decrease in polarizability across the series is anticipated.…”

Poole‐Frenkel electrical conduction in europium oxide films deposited on Si(100)

“…If we consider the static value ε ox = 13.9 [19], then the theoretical values of these coefficients are β Sc = 1.02x10 -5 eV.m .V -1/2 . Hence, the experimental value of β is closer to the calculated β PF value.…”

Dielectric and Raman studies of Ba0.06(Na1/2Bi1/2)0.94TiO3–NaNbO3ceramics

“…a large crystal radius, high effective number of electrons and presence of lone pair electrons in the outer shell. Fortunately, bismuth (Bi) has high polarizability (>5Å 3 ) [9]. Also, it is non-toxic and has no harmful effect on environment.…”