UV–visible absorption spectrum determination of optical energy gaps of α and β lithium nitrides

It is well known that a high pressure can induce α–β phase transformation of lithium nitride (Li3N). However, this work demonstrated that a reverse phase transformation of Li3N from β to α could occur when it was subjected to heat-treatment at 500 °C in vacuum. Furthermore, the optical properties of α and β lithium nitrides were evaluated by UV–visible spectra. The optical energy gaps (Eg) of α and β lithium nitrides, which were determined from the derivative UV–visible spectra, are 1.81±0.01 and 2.14±0.01 eV, respectively.

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► Reverse phase transformation of Li3N from β to α was revealed.
► Optical energy gap of β-Li3N was first determined by experiments.
► Measured energy gaps demonstrated that both α-Li3N and β-Li3N are semiconductors.