The Arrhenius plots of heterogeneous solids comprising of lithium aluminum titanium phosphate (LATP) glass-ceramic, Al2O3, and Ba0.6Sr0.4TiO3 (0.6 BST) exhibit an inflection or peak around 27 degrees C, which is interpreted as a signature of space charge. The space charge is formed by the adsorption of lithium ions onto the dielectric phases below 27 degrees C. The space charge is also a source of an electric field, which influences the transport of conducting ions. The adsorbed ions are desorbed above 27 degrees C, resulting in a reduction or elimination of the space charge effect. A high dielectric constant phase, 0.6 BST, retains the space charge effect even at temperatures greater than 27 degrees C.