Mechanocaloric materials undergo sizable temperature changes during stress-induced phase transformations and?hence are highly sought after for solid-state cooling applications. Most known mechanocaloric materials, however, operate at non-ambient temperatures and involve first-order structural transitions that pose practical cyclability issues. Here, we demonstrate large room-temperature mechanocaloric effects in the absence of any structural phase transformation in the fast-ion conductor Li3N ( ΔS ~ 25?J?K?1?kg?1 and ΔT ~ 5?K). Depending on whether the applied stress is hydrostatic or uniaxial the resulting caloric effect is either direct (ΔT??0) or inverse (ΔT??0). The dual caloric response of Li3N is due exclusively to stress-induced variations on its ionic conductivity, which entail large entropy and volume changes that are fully reversible. Our work should motivate the search of large and dual mechanocaloric effects in a wide variety of superionic materials already employed in electrochemical devices.
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