Measurement of the isothermal and adiabatic dielectric constant of TGS

With a high-precision digital lock-in amplifier with digital drift correction, spectra of the dielectric constant of TGS have been measured. With a digital realization of a lock-in amplifier, measurements of the dielectric constant can be performed down to frequencies of 10^-3 Hz. The dielectric constant is usually measured at frequencies above the thermal relaxation frequency too, thus realizing isothermal conditions. To separate the influence of domain and conductivity effects, the thermal time constant of the sample has been varied. Spectra of the dielectric constant are measured with variable coupling of the sample to a heat sink of liquid paraffin. The influence of the entropic contribution to the dielectric constant is directly determined from these spectra