  In this work, we present the possible existence of thermal phase transition
between AdS to dS asymptotic geometries in vacuum in the context of novel 4D
Einstein-Gauss-Bonnet (EGB) gravity. The phase transition proceeds through the
thermalon (the Euclidean sector of the bubble thin-shell) formation having a
black hole inside the interior of dS spacetime and a thermal AdS spacetime in
the exterior without introducing any matter field. According to our analysis,
we find that the gravitational phase transitions using novel 4D EGB gravity
always take place for all existences of the 4D EGB coupling. In contrast to
5-dimensional EGB gravity, the existence of phase transition requires a narrow
range of the 4D EGB coupling with particular critical values, while the
5-dimension sector has a wider range of its coupling for the existences of the
thermalon and there also exist critical values for the emergence of the phase
transition.
