High-Resolution Thermal Expansion of MgB2

The thermal expansion of polycrystalline MgB2 from 5–300 K is studied using high-resolution capacitance dilatometry. The thermal expansivity exhibits a small jump of −5.8×10−8 K−1 at Tc (in accord with expectations from the Ehrenfest relationship and published specific heat and pressure data) and a negative peak-like feature close to 5 K. No indications of any structural instabilities are observed.