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.

A series of undergraduate laboratory experiments that utilize reversed-phase HPLC separation, inductively coupled plasma spectroscopy (ICP), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) are described for the analysis of commercial sunscreens. The active ingredients of many sunscreen brands include zinc or titanium oxide in addition to organic acids. Students determine the zinc content using ICP, and the chemical composition as well as particle sizes using SEM-EDS. The organic UV absorbers octocrylene and oxybenzone are quantified using HPLC. With the incorporation of these interesting characterization techniques in second or fourth-year chemistry courses, and by having students analyze sunscreen samples that are medically relevant in terms of health effects, students engage in timely research and at the same time gain exposure to a variety of instruments in the analysis of a familiar household product.

Pressure tuning is a potentially useful tool to increase the rate of discovery of solid-state materials with improved properties. The interaction parameters that determine the properties of a given material define a phase space, which can have one or more dimensions. A single solid-state compound can be represented by a single point in this phase space. The traditional approach to the search for new materials involves an exploration of phase space by sequential synthesis and characterization of new solid-state compounds. Because materials interaction parameters (e.g., orbital overlap, orbital energy, magnetic coupling, etc.) can be tuned with pressure, phase space can also be traversed with pressure, potentially allowing a property of interest to be optimized. The advantages of pressure tuning include the ability to tune rapidly and cleanly, typically without introducing disorder, phase separation, or other complicating factors. Demonstration of the existence of materials that exhibit improved properties at high pressure can provide insight into the structural and electronic parameters necessary for such improved properties to guide the search for such behavior at atmospheric pressure.

The interaction parameters that determine materials properties are generally sensitive to pressure. Thus, pressure tuning provides a means to rapidly explore a material's interaction parameter phase space to increase the rate of discovery of materials with improved properties. Here we report a significant improvement in the thermoelectric properties of the Kondo insulator Nd x Ce 3-x Pt 3 Sb 4 upon pressure tuning to 2 GPa. This result provides a target for synthetic attempts at ambient pressure to duplicate the observed improved high-pressure behavior.