There is widespread interest in the search for materials that would allow the fabrication of more efficient thermoelectric devices for cooling and power generation applications. Here, we report a large increase in the thermoelectric power of p-doped antimony bismuth telluride alloys upon pressure tuning under nonhydrostatic compression conditions. Together with measurements of the electrical conductivity and an upper bound estimated for the thermal conductivity under pressure, these results indicate that values of the dimensionless thermoelectric figure of merit, ZT, in excess of 2 have been achieved, substantially larger than the best observed values in bulk materials to date. We suggest an explanation for the observed behavior and strategies for attempting to reproduce it at ambient pressure.

We have studied Zn(CN) 2 at high pressure using Raman spectroscopy, and report Gruneisen parameters of the soft phonons. The phonon frequencies and eigen vectors obtained from ab-initio calculations are used for the assignment of the observed phonon spectra.Out of the eleven zone-centre optical modes, six modes exhibit negative Gruneisen parameter. The calculations suggest that the soft phonons correspond to the librational and translational modes of C≡N rigid unit, with librational modes contributing more to thermal expansion. A rapid disordering of the lattice is found above 1.6 GPa from X-ray diffraction.

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We are aware of the metallization of G-type antiferromagnetic BaMn 2 As 2 by light doping of K at the Ba site 1 and the possibility of pressure-induced metallicity at 16 GPa in the related correlated insulator LaMnPO. 2 It has also been seen recently that metallization can also be achieved in insulating LaMnAsO by chemical substitution of Sr at the La site, for a Sr fraction x 0.08. 3 We regret that these papers were not cited in our own.