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Gläser und Glaskeramiken (β‐Eukryptit) mit Zusammensetzungen nahe der von stöchiometrischem L120°C A1203°C 2 SiO2, z.B. LiAlSiO4 , sind, wie aus Messungen der Ionenleitfähigkeit (25‐650°C) hervorgeht, bei hohen Temperaturen gute Litleitende Festelektrolyte (bei N 600°C etwa l0" (ohm′ cm)" ).

In this Letter we present measurements of the attenuation and velocity of ultrasound in liquid 3 He at temperatures below 3 raK and at various pressures" In this temperature region and in the presence of solid 3 He, two new phases with extraordinary NMR properties were discovered by Osheroff et al. 1 In this same temperature region Webb et al. 2 observed a second-order phase transition, a discontinuity but not a divergence in the specific heat, over a wide range of pressure in liquid 3 He. This phase transition has been associated with the higher-temperature phase transition found in Ref. 1. The lower temperature phase has not yet manifested itself in our experiments. The present measurements were made in zero magnetic field at a variety of pressures from 140 lb/in 0 2 to near the melting curve and, where possible, at 5, 15, and 25 MHz 0 For these frequencies we have the relation oor > 1, where r 1514 (1972). is a collision time, in the low-temperature region of interest. The conditions for measurement at least approximate those for propagation of zero sound 3 * 4 for T>T C and may approximate at our lowest temperatures the conditions for propagation of a density fluctuation mode in a superfluid neutral Fermi fluid as discussed by Leggett 0 5 The 3 He was cooled using an epoxy-walled, cerium magnesium nitrate (CMN)-filled, demagnetization cell of standard design 6 in which the sonic cell was lodged in a cylindrical cavity in the CMN. Sonic measurements were made using the method of Abel, Anderson, and Wheatley. 7 The nature of the experimental data and their treatment are given by Wheatley 8 (see sect. 2.4). The sound is propagated through the 3 He between two 5-MHz epoxy-backed X-cnt quartz crystals separated by a 0 o 4996-cm-longx0 o 76*cm-i.d o Measurements of attenuation and velocity of sound in the collisionless regime have been made in normal and extraordinary phases of liquid 3 He at several pressures. The attenuation has a frequency-independent component with a sharp maximum just below T c and a frequency-independent component with a BCS-like temperature dependence. The velocity, frequency dependent very near T c , becomes frequency independent at lower T and may be approaching the velocity of first sound. 829

The thermal conductivity K of pure He 3 and of two dilute solutions of He 3 in He 4 has been measured from 30 down to 5 mdeg K or below. For pure He 3 , KT increases with increasing temperature. For the dilute solutions at low enough temperatures, K is consistent with the T~i temperature dependence of a normal Fermi liquid, but the magnitudes of KT do not agree with values computed from an effective potential based on spin-diffusion coefficient measurements.We have measured at saturated vapor pressure the thermal conductivity both of pure liquid He 3 and of the same two dilute solutions of He 3 in He 4 for which measurements of specific heat, spin-diffusion coefficient, and magnetic susceptibility have already been reported. 1 The results relate to the question of the anomalous behavior of pure He 3 at low temperatures 2 ' 3 and to the effective interactions between He 3 quasiparticles in the dilute solutions. 4

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A specific-heat "discontinuity" is observed in. liquid He from 241 lb/in. 2 to the melting pressure in the temperature range 2 -3 mK.In measurements along the melting curve of He', using an adiabatic compressional cooling device, Osheroff Because of the sharpness of the transition, both the actual value of the transition temperature and the specific-heat jump were usually obtained using a second type of measurement in which the cell contents were allowed to drift through the transi-

The thermal resistance in both superfluid phases of 3He has been measured at 20.0 and 29.6 bar in zero magnetic field. Heat conduction in 3He-B is shown to be primarily hydrodynamic, and a regime of reproducible heat flow behavior in the A phase is reported. The viscosity of each phase as a function of temperature is calculated using an equation of the two-fluid model, and critical velocity effects are discussed.

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