Dielectric constant κ′, loss κ″, and conductivity σ of single crystals of CoO, NiO, and mixed crystals of CoO–NiO as a function of frequency from 102 to 1010 cps and temperature from −193°C to 400°C have been determined. The dielectric constant κ′ is constant (12.9 at 25°C) in the whole frequency range in CoO. It decreases with frequency in NiO and mixed crystals CoO–NiO. In NiO κ′ reaches a constant value (11.9 at 25°C) at 105 cps, and in CoO·NiO (12.3 at 25°C) at 1010 cps. The dielectric constants extrapolated to 0°K are 10.9, 10.0, and 9.1 for CoO, CoO·NiO, and NiO, respectively. In all crystals the dielectric constant increases exponentially with temperature. Using modified Debye equations, two thermal activation energies for κ′ have been obtained: 0.042, 0.027, and 0.018 eV for temperatures below 40°C (frequency-independent region); 0.33, 0.20, and 0.16 eV for temperatures above 40°C, for CoO, NiO, and CoO·NiO (frequency-dependent region). The plot of log σ vs 1/T gives straight lines for CoO from 400° to 100°C, and NiO from 400° to 25°C with activation energies 0.73 and 0.66 eV. At lower temperatures the activation energies decrease continuously. The mixed crystals have two activation energies, one at high temperatures and the other at low temperatures. Variation of the activation energy with composition at high temperatures is less than that at low temperatures. The variation of activation energies in mixed crystals is correlated to lattice distortion and an increase of trivalent ion concentration.

The room-temperature reststrahlen spectra of flame fusion grown NiO and CoO, as well as those of three intermediate members of this solid solution series, are presented. A full Kramers-Kronig analysis on all members has been performed and checked with damped oscillator calculations. The resulting refractive indices, extinction coefficients, dielectric constants, effective ionic charges (Szigeti q*), and characteristic frequencies are presented along with the lattice constants and are discussed in the light of their interrelation.

Die Arbeit enth~lt auBer den in der Zusammenfassung zusammengestellten Tatsachen das Absorptionsspektrum eines liehtelektriseh leitenden KC1-Kristalls im erregten und unerreg~en Zustand. Ferner berichtigt sie in w 7 den Irrtum, dat] ~ich Alkalihalogenide mit Fremdf~rbung erster Art in eine Reihe abnehmender ttal~barkeit im Liehte ordnen lassen.

Dielectric constant κ′ and dielectric loss κ″ of CaF2, SrF2, and BaF2 single crystals were determined as a function of frequency from 102 to 106 (partly to 1010) cps, in the temperature range from –193° to 500°C. κ′ in all three crystals is frequency independent at 25°C. The dielectric loss κ″ varies only slightly with frequency, having the greatest values at lowest and highest frequencies. The temperature has a striking effect on κ′ and κ″. κ′ increases continuously from 6.4, 6.1, and 6.9 (extrapolated values at absolute zero) to 8.07, 7.70, and 8.46 at 500°C at frequencies above 106 cps for CaF2, SrF2, and BaF2, respectively. Below about 25°C, κ′ is frequency-independent; at higher temperatures it increases with decreasing frequency, κ″ increases with temperature exponentially and decreases with frequency. A detailed interpretation of the frequency and temperature influence on κ′ and κ″ is given. Using expansion and density variation with temperature, a separation of electronic from atomic and dipolar contributions was made. The total dielectric constant is subdivided into six terms (three electronic and three atomic).