Specific Heat Measured at High Pressures by a Pulse Method

Abstract

The classical electric pulse technique has been adapted to measurements of specific heat at high pressure. A wire specimen is heated by a 100 μsec pulse, stabilized at I = 50 A. The resulting temperature rise is extracted from the voltage drop U over the sample by means of a bridge circuit. The specific heat is obtained from the formula c_p = C(T,P)U I / m ė, where C(T,P) is a function to be experimentally determined for a given sample, m the mass of the sample, and ė the time derivative of the bridge output voltage. A procedure has been developed for in situ corrections of ė for heat loss to the medium surrounding the wire. Digital techniques are used for the pulse analysis. The method has been used to ascertain the pressure dependence of c_p for Cu up to 100 kilobars at room temperature. The relative change in c_p was found to be 2.8 × 10⁻⁴/kilobar.