Projected electrostatic and absorptive potential profiles across intergranular glassy films (IGFs) and interfaces between grains and glassy pockets in silicon nitride ceramics were obtained by reconstructing the electron exit face wave function from a series of defocused TEM images. The phase-object approximation (POA) was used for extracting the projected potential from the complex-valued exit-face wave function. The electrostatic as well as the absorptive potentials were scaled with respect to vacuum. For La 2O3-MgO doped Si3N4, the potential profiles across the grain/glassy pocket interface and the IGF were observed to be very similar and give very strong evidence for the existence of a space charge layer at the interface.