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Time resolved nonlinear dielectric effect in terms of Δln(tan δ) at 1 kHz for PC at T = 166 K. Symbols represent the uncorrected experimental results from Ref. 2, the solid and dashed lines are for the model calculations which differ only in the high frequency dielectric constant used, ɛ ∞ = 3.40 and 5.75, respectively. In this case, the value of ΔC p is treated as adjustable parameter of the model. Results are displayed for the 60 periods following the transition from a peak field of E 0 = 15.6 kV/cm to E 0 = 78 kV/cm at t = 0 and the 20 periods following the transition back to the low field at t = 0.06 s.
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Calculation of the frequency resolved dielectric loss factor, tan δ, and its field induced changes based on parameters matching the behavior of PC at T = 166 K as in Fig. 1. As indicated, the solid and dashed lines are for the model calculations which differ only in the high frequency dielectric constant used, ɛ ∞ = 3.40 and 5.75, respectively. Within this range, changing ɛ ∞ by 69% generates a discrepancy in Δln(tan δ) limited to 9% of their peak values. The loss factor itself (marked “tan δ”, scaled arbitrarily), is shown as short dashed line.
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A dielectric cell with a Teflon spacer covering the entire perimeter is advantageous for impedance experiments performed at electric fields of 450 kV/cm or more using a 10 μm electrode separation. While the large spacer surface makes a correction to the infinite frequency dielectric constant necessary if reliable permittivity data are desired, field induced relative changes are extremely insensitive to this problem. It is demonstrated that the field induced relative changes of the loss factor, tan δ, with and without correcting for the excess parallel capacitance are practically the same.
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