The major defects in KCl are known to be Schottky-type and the formation free energy of the cation vacancy is lower than that of the anion vacancy. Sketch the surface charge and surface defect concentration in pure KCl and in highly CaCl2-doped KCl. Sketch and explain the change in defect concentrations with temperature (in a scale of 1/T) in the bulk of a CaCl2-doped KCl.