Piezoelectricity in half-Heusler narrow-bandgap semiconductors.

Piezoelectricity is primarily observed in noncentrosymmetric insulators or wide bandgap semiconductors. We report the observation of the piezoelectric (PE) effect in half-Heusler (HH) narrow-bandgap semiconductors TiNiSn, ZrNiSn, and TiCoSb. These materials exhibit shear PE strain coefficients that reach ~38 and 33 picocoulombs per newton in ZrNiSn and TiCoSb, respectively, which are high values for noncentrosymmetric nonpolar materials. We demonstrated a TiCoSb-based PE sensor with a large voltage response and capable of charging a capacitor. The PE effect in HHs remains thermally stable up to 1173 kelvin, underscoring their potential for high-temperature applications. Our observations suggest that these HH narrow-bandgap semiconductors may find promising applications for advanced multifunctional technologies. Editor's summary: Piezoelectric materials generate electricity when strained and are useful as sensors or actuators. For a variety of reasons, materials that are good piezoelectrics are electrical insulators or wide bandgap semiconductors. Huang et al. show that narrow bandgap semiconductors from the half-Heusler family can also have attractive piezoelectric properties. They found at least three lead-free compositions with good piezoelectric strain coefficients, even at high temperatures. The particular combination of properties make these materials good candidates for a different range of applications than traditional piezoelectrics. —Brent Grocholski [ABSTRACT FROM AUTHOR]