We present a novel experimental design for high sensitivity measurements of the electrical resistance of samples at high pressures (0-6GPa) and high temperatures (0-1000K) in a ’Paris-Edinburgh’ type large volume press. 

Uniquely, the electrical measurements are taken directly on a small sample, thus greatly increasing the sensitivity of the measurement.  This sensitivity to minor changes of the sample's electrical resistance can be used to clearly identify solid-liquid, solid-solid and possibly liquid-liquid phase transitions.  Electrical resistance measurements are relatively simple and rapid to execute and the efficacy of the present experimental design is demonstrated by measuring the electrical resistance of Pb, Sn and Bi across a wide domain of temperature-pressure phase space and employing it to identify the loci of phase transitions.

Based on these results the phase diagrams of these elements are reconstructed to high accuracy and found to be in excellent agreement with previous studies.  In particular, by mapping the locations of several well-studied pressure-temperatue points in the phase diagram of Sn and Bi, it is demonstrated that a standard calibration exists for the temperature and pressure.  Thus it eliminates the need for direct or indirect temperature and pressure measurements. 

The present technique allows a simple and accurate mapping of phase diagrams under extreme conditions and may be of particular importance in advancing studies of liquid state anomalies.