Phase transformation of molybdenum trioxide to molybdenum dioxide: An in‐situ transmission electron microscopy investigation

Abstract We use in‐situ environmental transmission electron microscopy ( ETEM ) to investigate the phase transformation of α‐MoO ₃ in vacuum. In‐situ selected area electron diffraction ( SAED ) indicates that α‐MoO ₃ directly transfers to monoclinic MoO ₂ without intermediate phase; however, high resolution transmission electron microscopy ( HRTEM ) study reveals that Mo ₄ O ₁₁ precipitates on the surface of MoO ₂ matrix. Judging from the size of Mo ₄ O ₁₁ and its orientation relationship with MoO ₂ , we believe that the formation of Mo ₄ O ₁₁ is due to the reaction between MoO ₂ and the untransformed MoO ₃ .