Dielectric relaxation processes in smoky quartz crystals at very low temperatures

Abstract

CRYSTALSThe relaxation time governing the dielectric loss of smoky quartz crystals appears to level off as a function of temperature below 12OK, approaching a value of about 1 msec. The relaxational behaviour of the colour centres is discussed in terms of tunnelling processes.Under favorite conditions, lattice imperfections at which electrons are trapped (e.g. colour centres) may exhibit a Debye type dielectric response [1,2]. A very clear case is found with smoky quartz crystals [3], which has recently been reinvestigated [4] by the present authors, especially between 20 ° and 160OK. In this letter we wish to report our measurements on the temperature dependence of the dielectric relaxation time extended downwards to 4°K, using the same specimen, with E //c-axis.According to the well-known Debye relaxation theory the dielectric loss factor tg 8 as a function of frequency and temperature should follow the expression 4~ {E + 2~ 2 Np 2 wTin which e is the dielectric constant of the matrix, N and p the concentration and dipole strength of the centres, and T the absolute temperature.

Electronic dipole resonance in smoky quartz

“…In the dielectric constant of the solid a Langevin-type of contribution may then be found and Debye-type dielectric relaxation losses may occur which are determined by a temperature dependent relaxation time governing the dynamics of the dipole orientation [1][2][3][4][5]. The wave function of the trapped electron may be thought to be a linear combination of atomic wave functions, centred at certain equivalent lattice sites.…”

Calorimetric measurement of very low dielectric loss at low temperatures

“…2 " ~~ and claim an accuracy in 6 to about k 10-6 at 50 Hz; evidence appearing in the Appendix to the present paper, however, tends to indicate that this estimate may be considerably optimistic. Volger et al (1955), Volger and Stevels (1956), Stevels and Volger (1962) and de Vos and Volger (1967b) have reported the audio-frequency losses down to 1 4 " ~ of fused silica and other glasses, and of various samples of crystalline quartz; de Vos and Volger (1967a) have also published results for smoky quartz down to about 4 ' ~. Ioffe gave figures above about 1 2 " ~ for glasses (e.g.…”