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Dielectric permittivities and losses for 1,2‐ethanedithiol, 1,2‐propanedithiol, and 1,2‐dichloropropane in the liquid state have been measured at 1.62, 3.17, and 3.49 cm in the microwave region at different temperatures. The distribution parameter in 1,2‐propanedithiol was found to increase with increasing temperature in contrast to that in 1,2‐ethanedithiol and 1,2‐dichloropropane. A possible explanation for this has been suggested. The energy differences between the trans and gauche isomers in all the liquids obtained from the dipole moment measurements agree fairly well with those obtained from spectroscopic studies.

Toughened PVC systems prepared on the basis of Hostalit H-9970 (Hoechst AG) were studied by dielectric depolarization spectroscopy. The spectra obtained as a function of the temperature were compared with dynamic mechanical and dielectric relaxation spectra and with thermomechanical curves. The dielectric depolarization peaks were found to correlate with the structural transitions measured by mechanical and dielectric spectroscopy. Auf der Basis von Hostalit H-9970 (Hoechst AG) hergestellte schlagfeste Polymeren-Systeme wurden durch dielektrische Depolarisationsspektroskopie untersucht. Die in Abhangigkeit von der Temperatur aufgenommenen Depolarisationsspektren wurden mit den dynamisch mechanischen und dielektrischen Relaxationsspektren und mit thermomechanischen Kurven verglichen. Ein enger Zusammenhang wurde zwischen den dielektrischen Depolarisationsmaxima und den durch die mechanische und dielektrische Spektroskopie gemessenen Strukturumwandlungen beobachtet.

The dielectric properties of a series of semiconducting polyazophenylenes were studied as a function of temperature and molecular weight in the temperature range 293–600°K and for molecular weights between 5,100 and 62,800 at a constant frequency of 1 kHz. The compounds studied included poly-2,4-diaminotoluene, poly-2,4-diaminoanisole, and poly-2,5-diaminotoluene. The dielectric properties are presented in the usual way in terms of a complex dielectric constant e* = e′—je″. Activation energies of relaxation processes were evaluated from the areas and widths of the dielectric loss factor, e″, against reciprocal temperature at constant frequency. The dielectric activation energies were found to be roughly equal to the activation energies from the DC conductivity. This indicates that the conduction mechanism is based on rotational movements of molecules or parts of molecules.

Recent advances in dispersive Fourier spectrometry are described. The complex refractive indices of lossy materials are now directly measurable over a wide spectral range which extends from rnicrowavelengths to the midinfrared. Some results for liquid ethanol and butanol are presented and interpretation of the spectra in terms of hydrogen bonding is offered.

Expressions for the static dielectric permittivity analogous to the Kirkwood-Frohlich equation are derived for liquid crystals with uniaxial symmetry.

There are three methods for the determination of the dielectric properties of material in sheet form: the Hartshorn-Ward 'resonance-substitution' technique (BS 2067), the Lynch method using a transformer bridge (BS 4542) and the two fluid immersion method. These methods may be used at frequencies up to 1 MHz, and, in this range, it is shown that the two fluid immersion method offers advantages for permittivity measurement but is not suitable for determination of tan ?. A modified form of Q meter is then described for use in the frequency range 1-100 MHz where application of the resonance substitution method permits dielectric loss measurements to be made with a precision of better than five microradians. Measurements at microwave frequencies are made by resonant cavity techniques and comparison is made between the value of permittivity determined at 1 MHz by a cross checkable two fluid method, and those calculated from the high frequency values of permittivity and dielectric loss.

Convenient, tunable, sealed‐off cavity resonators are described at frequencies of 1, 2, 9, and 24 kMc, for use with internal pressures up to 1000 psi. The modes of oscillation employed were TE01n, TE11n, and TM01 hybrid, all in a circular cylinder. A convenient method for sealing an iris, applicable over a wide‐frequency range, is to insert a tapered Teflon plug. A Kovar‐glass seal for coaxial lines is described that provides a good impedance match in a 50‐ohm line. The measuring procedure is described. Accuracy of dielectric loss measurements was increased by calibrating the loss changes of the cavity arising from reresonating it upon admission of lossless gas.

For systems containing polar molecules it has been found that there is a wave-length region in which the dielectric constant decreases with increasing frequency. This wave-length region, dependent upon the size of the orienting molecule and the viscosity of the medium, determines a time of relaxation for the polar molecules which has been evaluated by Debye using the law of Stokes for the rotation of a particle in a viscous medium. The purpose of the present research is to test the dipole theory by making measurements of the frequency variation of the dielectric constant for viscous solutions of various polar substances in nonpolar solvent media. To this end it was necessary to devise an accurate method of measurement for the dielectric constant of a liquid system at frequencies as high as 2\ifmmode\times\else\texttimes\fi{}${10}^{7}$ cycles per second. The apparatus used is briefly described. The dielectric constants of rosin solutions in mineral oils of varying viscosity are tabulated and calculations for the inner-frictional constant for these systems are made. The effect of viscosity upon the behavior of mixtures of "floricin," paraffin oil and vaseline is also investigated. It is found to have little effect, a fact of considerable interest with regard to the inner structure of these solutions. An explanation for the failure to observe an expected dispersion in several experiments is attempted. The comparison of the experimental results with the requirements of the Debye theory leads to several interesting conclusions. There are objections to the use of the ordinary coefficient of viscosity of the medium to measure the frictional resistance to the rotation of a molecule when the discontinuities of the fluid are large compared with the size of the rotating particle and probably in other cases as well. Calculations from the experimental data make possible a differentiation between systems in which the suspended particles are all of one size or monodisperse, and in which they are polydisperse. Finally, there is suggested the type of experiment which must be made if a quantitative verification of the theory is sought.

The complex dielectric constant of NaNO 2 crystal was measured in a frequency range between 1 MHz and 24 GHz from room temperature to 210°C. The measuring methods in the various frequency ranges were described in detail and especially the measuring accuracies in the complex dielectric constant and the temperature were considered closely. It was found that a dielectric dispersion occurs in the ferroelectric b direction and this dispersion obeys nearly the formula of the Debye-type with a single relaxation time above the transition point. The relaxation frequency is proportional to ( T - T 0 ) near the transition point, where T is the temperature and T 0 is about 162°C, and deviates from this linear relationship above ca 180°C, bending upward. In the a and c directions, any remarkable change in the dielectric constant was not observed up to 24 GHz.

A number of diagrams is presented for deducing the value of the complex dielectric constant in an exact and straightforward way.

The static dielectric constant and dielectric loss for the binary solutions of thermacol in various organic solvents have been measured varying the concentration of solute. The dielectric constant varied linearly with the concentration of solute, whereas the dielectric loss showed excess peak at a certain concentration of the solute for binary solutions. The authors also performed the first-principles calculations to study the equilibrium configurations of ethyl acetate and n-butyl acetate and estimated dipole moments. The experimental values of dipole moment for ethyl acetate and n-butyl acetate agreed fairly well with those calculated from first-principles. Key words: Dielectric constant; Dielectric loss; Binary solution; Dipole moment DOI: http://dx.doi.org/10.3329/jbas.v35i2.9427 JBAS 2011; 35(2): 211-220

THE MEASUREMENT of the complex dielectric constant of very-high-dielectric-constant materials at microwave frequencies is considerably more difficult than the measurement of materials with a low dielectric constant. The reason for this can be best illustrated by consideration of a commonly used method of measuring dielectric constant at microwave frequencies which is called the short-circuited line method. The equipment used is shown in Fig. 1.1,2 The test sample is placed against a fixed short circuit, and the voltage standing wave ratio (VSWR) and location of the voltage minimum are measured. The complex dielectric constant can be calculated from these measurements. This method is satisfactory for materials where the real dielectric constant is relatively low, but poses serious difficulties for materials where the real dielectric constant is very high. In discussing the reasons for the difficulties, low-loss samples and high-loss samples will be considered separately.

The writer has already published in a previous issue of the PROCEEDINGS a new method of measuring resonant impedance and radio-frequency resistance as applied to broadcast frequencies. In the present paper he gives, as another example of its application, some results obtained from the measurement in a band of high frequencies extending from 6300 to 26,300 kilocycles. It is ascertained that the additional dielectric loss, which is introduced into the resonant circuit by using a screen-grid tube as a dynatron, exercises only a slight influence on the measurement. The constants of the resonant circuit alone may be derived from those of the circuit combined with the tube, which can be measured directly. The correctness of the result is varified by the aid of a known value of the additional series resistance. Finally some remarks on short-wave amplification are given as a result of measurements.

The dielectric constants and loss angles of a series of concentrated aqueous ionic solutions have been measured at wave‐lengths of 10 cm, 3 cm, and 1.25 cm. From these results the values of the static dielectric constant and relaxation time for these solutions have been calculated on the basis of the Debye formula, which appears to hold accurately. All salts show a lowering of the dielectric constant and a shift in the relaxation time of water. It is found that the dielectric constant e can be represented by a formula e=eω+2δc, where eω is the dielectric constant of water, c is the concentration in moles per liter, and δ has values between −7 and −15 for various salts in concentrations of up to 2 M.In Part I the measurements are described and the results discussed in relation to the structure of ionic solutions. In Part II the validity of the Debye‐Sack saturation theory of the dielectric constant and the effects of the fall of dielectric constant on the electrolytic properties of concentrated solutions ...

A new method of measuremeing dielectric properties such as relaxation time of dipole, its activation energy and dielectric constant in very low frequency (less than 0.1 Hz) by thermally stimulated current (TSC) is described. Relations between the dielectric properties and TSC are theoretically analyzed, and experimental results on SiO2 films are illustrated. It is shown that this method is more useful than the other methods in the measurement of dielectric properties due to dipoles having the distributed relaxation time and the activation energy. The distribution of the activation energy on SiO2 films was obtained by computer calculation.

Dielectric constant and dielectric loss (e′ and e″) of four liquid alkanethiols have been measured at four microwave frequencies at 0, 20, 40, and 60°C. The normalized plots of e′/(e0−e∞) vs (e′−e∞)/(e0−e∞) for all four liquids are skewed arcs. The characteristic relaxation time (τ0) and empirical parameter (β) have been calculated from these plots. The dielectric behavior of alkanethiols is more like alkyl halides than alcohols. The main mechanism which is responsible for asymmetric distribution of relaxation time in the liquid state appears to be multiple relaxation processes.

Experimental evidence now indicates that the microwave dielectric properties of solids are strongly influenced by the infrared active phonon modes. The “real dielectric constant”, e′, of polar materials, i. e. those in which ɛ′ is noticeably greater than the square of the optical index of refraction, exhibits a temperature dependence dominated by the change of integrated infrared absorption. The microwave dielectric loss, ɛ″, is influenced by the low frequency “tail” of the infrared resonance type absorption, as may be inferred from the monotonic increase with temperature and proportionality to frequency. It is suggested that the one dimensional coupling of the electric field to the acoustic modes of a dielectric solid would lead to additional low frequency “background” dielectric losses which are essentially frequency independent, in agreement with experimental observations.

A method is described for measuring dielectric losses at microwave frequencies in materials with a large dielectric constant. By observing a dielectric resonance in a sufficiently large sample, the loss tangent of the material can be obtained. Results on SrTiO/sub 3/, single crystals at 20 kMc are presented.

Three specimens of rutile were prepared and the dielectric properties studied over a range of frequency and temperature. A dielectric constant of approximately 100 was found which remained substantially constant through the highest radiofrequencies, falling off only in the infra‐red region. The dielectric losses are low, particularly at the higher frequencies. The dielectric constant decreases with increasing temperature, having an average temperature coefficient of −8.2×10−4/°C. An exponential relationship between conductivity and the reciprocal of the absolute temperature holds for rutile in the higher temperature region. Mixtures of rutile powder with other dielectric materials obey a logarithmic mixture formula. Two mechanisms which have been proposed to explain the high dielectric constant of rutile are discussed. A simple mechanism based on the Clausius‐Mosotti equation is described.

A method for measuring the dielectric constant and conductivity of powders is described. Numerous formulas of earlier workers pertaining to the dielectric constant of porous media of low density are discussed. It is then shown that these relations incorrectly predict a value of the intrinsic dielectric constant which is a function of density. In an effort to develop a formula which would predict correctly the density dependence to at least a medium range of densities, a calculation is presented which expresses the effective dielectric constant of a given system as a function of particle shape, intrinsic dielectric constant, powdered density, and packing properties of powders composed of ellipsoidal particles. The formula involves the demagnetization coefficient and intrinsic dielectric constant of the powder particles. Data obtained from measurements of dielectric constant of magnetism oxide, silica, polystyrene, zinc oxide, etc., were applied to this formula and the intrinsic dielectric constants inferre...

An attempt is made to investigate the transition from resonance to relaxation spectrum by high‐pressure research in the microwave region. Equipment has been developed for studying the dielectric constant and loss of gases and liquids in the K‐band region up to 1000 atmospheres at temperatures up to 300°C. Measurements on a nearly spherical molecule of strong dipole moment (CHClF2), on a linear molecule of weak dipole moment (N2O), and on mixtures of CHClF2 with nitrogen are reported and a preliminary discussion of the results is given.

The problem of evaluating dielectric constant and loss tangent by the short-circuited-waveguide technique has been encountered continually in recent years in the study of artificial dielectric media and radome materials. In general, practical measurements have involved materials with low loss and dielectric constants less than 10. The analytical method normally applied to data on such materials requires laborious computation. The available graphical methods have not completely eliminated computation and have provided answers of unsatisfactory accuracy. The present paper describes rapid graphical techniques for evaluating dielectric constant and loss tangent from the quantities normally measured with the slotted line, using samples of arbitrarily chosen length. It begins with equations previously derived for the case of low-loss media. By use of a new parameter, the relationship between dielectric constant and the measured shift in standing-wave minimum is plotted in such a way that all possible values of dielectric constant within any predetermined range are read directly from the graph with no computation whatsoever. A graph can be readily prepared to apply over a full range of frequency to all sizes of rectangular waveguide.

The complex dielectric constant of Rochelle salt has been measured at frequencies from 2.5 to 13 GHz, and at 155 MHz. The measurements were made in a temperature range from -50 to 45\ifmmode^\circ\else\textdegree\fi{}C which includes the ferroelectric region and significant parts of both paraelectric regions. Measurements were made both with and without dc biases. The dielectric constant is found to undergo a relaxation of a strictly Debye character. Over the entire temperature range, the relaxation time is found to be proportional to ${T}^{1.25}$ times the difference between the low-frequency, clamped, differential dielectric constant and its limiting high-frequency value. This result is shown to be consistent with a model of the high-frequency dielectric behavior based on the Kubo susceptibility formalism. Following Mitsui, it is assumed that the ferroelectric properties of Rochelle salt arise from the rotation of hydroxyl groups within the tartrate molecules. The basic relaxation process probably involves phonon-induced transitions between the lowest states of these hydroxyl ions. However, the cooperative dipolar interaction between ions reduces the over-all relaxation rate of the coupled system. An approximate model Hamiltonian of the coupled hydroxyl system is constructed in terms of the Pauli matrices and is used to calculate an explicit expression for the relaxation rate.

Dielectric constant and dielectric loss at 3.8 GHz of six haloalkanes (viz. 1, 3-Dibromopropane; 1, 4-Dibromobutane; 1, 5-Dibromopentane; 1, 6-Dibromohexane; 1, 1-Dichloro-1-Nitroethane and 1, 1, 2, 2-Tetrabromoerhane) in solutions of a wide range of viscosities are reported in this paper. It is found that the plots of log τ s vs log η are not straight line. The data has been interpreted in terms of viscoelastic behaviour of the solvents.