H. E. Gunilla Knape

Brillouin spectra of the solid electrolyte Li2SO4

Brillouin spectra of single crystals of the solid electrolyte Li2SO4 were obtained for various crystal orientations in the temperature range 899–1120 K. The spectra contained one longitudinal component and at least one and sometimes both transverse components. The frequency shifts varied between 14.5 and 17.4 GHz for the longitudinal and between 4.1 and 9.0 GHz for the transverse component, the shift being strongly dependent on crystal orientation. The observed frequency shifts correspond to values of the elastic constants typical for plastic materials.

Hypersonic relaxation studies of molten zinc chloride

Brillouin spectroscopy has been used to study the frequency and temperature dependence of sonic waves in molten ZnCl2. The hypersonic velocity has been determined for two different scattering angles, 90.1° and 140.2°, and in the temperature range 294–741 °C, where a relaxation process was revealed. The sound absorption has been studied at temperatures lower and higher than those corresponding to the absorption peak. Shear and structural relaxations were both present with the same single relaxation time within experimental uncertainty. The temperature dependence of the longitudinal relaxation time was an Arrhenius type relation.

Solid sulphate electrolytes; the first examples of a strange ION transport mechanism

Abstract Neutron and X-ray diffraction studies reveal that fcc LJ2SO4, bcc LiNaSO4, and bcc LiAgSO4 are characterized by a strong rotational disorder of the sulphate ions which strongly enhances the mobility of the cations. Single crystal neutron scattering studies have been performed on fee Li2SO4 and the quasielastic scattering supports the previous conclusions, and more detailed information should be obtainable by this technique. The elastic constants of fee Li2SO4 have been determined by Brillouin scattering. The information obtained so far by Raman scattering concerning the motion of lithium ions in fcc Li2SO4 supports earlier conclusions from conductivity measurements.

Brillouin scattering and refractive index measurements in molten Li2SO4

Molten Li2SO4 has been investigated to determine the hypersonic velocity by use of Brillouin spectroscopy and the refractive index by an interferometric method. The hypersonic velocity and its temperature dependence has been determined at phonon frequencies around 13 GHz and in the temperature range 860–1000 °C. Values of the refractive index and its temperature dependence are presented in a temperature interval of ∼60 °C above the melting point at a wavelength of 4880 A.

Hypersonic velocities and compressibilities for some molten nitrates

The spontaneous Brillouin scattering has been used to measure the hypersonic velocity and its temperature dependence in a temperature range covering about 100 °C above the melting point in the nitrates: LiNO3, NaNO3, KNO3, RbNO3, CsNO3, and AgNO3. The investigations were performed in a frequqncy interval below any relaxation frequency in LiNO3 and NaNO3, while in KNO3 and AgNO3 the investigations were performed above some relaxation frequency according to comparisons with ultrasonic data. The measurements in CsNO3 and RbNO3 do not indicate any dispersion of the sonic velocity within the investigated frequency range and no conclusions can be drawn about relaxation effects as these molten alkali nitrates have neither been investigated hypersonically nor ultrasonically before. The measured hypersonic velocities were used for calculating the adiabatic and isothermal compressibilities as well as the specific heat at constant volume.

Hypersonic Velocity, Absorption and Relaxation in Molten CSNO3

Abstract Brillouin spectra of molten CSNO3 were investigated for scattering angles between 40 and 140° and in a temperature interval of 420-520 °C. An Ar+ singlemode laser was used for excitation and the total instrumental width was ~265 MHz. The measured frequency shifts and linewidths of the Brillouin components were used to determine velocities and attenuations of thermal sound waves in the frequency range 2.3-7.0 GHz. A dispersion of 4-5% was found between the present hyper sonic velocities and reported ultrasonic velocities. A considerable decrease in attenuation with frequency was observed in the investigated frequency range, with the value at high frequency ap proaching the classical attenuation. The results are in good agreement with Mountains theory of a single relaxation time. The relaxation time of the bulk viscosity coefficient was calculated to 1.2×10-10S.

Brillouin scattering measurements in molten AgNO3

Brillouin scattering studies have been carried out in molten AgNO3 at various temperatures (214-327 degrees C) and frequencies (3.5-11 GHz). Three types of data have been obtained: (i) hypersonic velocity data from the frequency shift of the Brillouin components; (ii) hypersonic absorption coefficients from the line-width of the Brillouin components; (iii) relaxation times of the bulk viscosity coefficient using a single relaxation theory. The experimental results of the acoustic attenuation are consistent with a relaxation curve calculated from the simplified form of the relaxation theory.

Determination of the Hypersonic Velocities in the Molten Salts NaNO3 and KNO3

Hypersonic velocities in the molten salts NaNO3 and KNO3 have been obtained by Brillouin scattering measurements. A He-Cd laser, 4416 Å, was used as a radiation source and the scattered light was analyzed with a pressure-scanned Fabry-Perot spectrometer. The temperature dependence of the sound velocity was determined in a temperature range covering some 100° above the melting point of the investigated salts. The obtained hypersonic velocity for NaNO3 was about the same and for KNO3 greater than reported ultrasonic velocities indicating that the measurements are performed in a frequency region below any possible relaxation frequency for NaNO3 and above some possible relaxation frequencies for KNO3

Notizen: Measurement of the Hypersonic Velocity in the Molten Salts NaCl and KCl

The hypersonic velocity of molten sodium and potassium chlorides has been measured over a temperature range of about 100°C above the melting points. The measurements were carried out at scattering angles 90° and 140°, corresponding to a 6-10 GHz frequency range. No deviation from previous ultrasonic values of velocity was observed at these frequencies, indicating that the measurements were performed at frequencies lower than any relaxation frequency.

Brillouin spectra of ethyl ether and ethyl alcohol

Measurements of Brillouin scattering in ethyl ether and ethyl alcohol were made for scattering angles of 42-150°. The spectra were excited by 4416 A radiation from an He-Cd laser and analysed with a pressure-scanned Fabry-Perot spectrometer. The measured frequency shifts and linewidths of the Brillouin components were used to determine the velocities and the lifetimes of thermal waves. The frequency range of the hypersonic waves was 26-59 GHz for ethyl ether and 26-68 GHz for ethyl alcohol. The measurements do not indicate any dispersion of the sonic velocity within the investigated frequency range and good agreement is obtained with earlier ultrasonic measurements.