thanku for your feedback sir ..can you pls attach some refernces

Please find the attached file for your reference.

Large sized ions r RE3+ ions (Pr3+, Sm3+ and Tb3+) acting as grain boundary activators . These ions, as the other RE3+ ions here, are mainly located at the surface of the ZnO grains and give rise to Schottky barriers at the ZnO grain boundaries.

In the case of Dy doped ZnO, Dy atom doped into a ZnO lattice effectively acts as a donor by supplying a single free electron when it (as a Dy+3 ion) occupies the site of a Zn+2 ion. Further increases in Dy2O3 content resulted in an obvious increasing resistivity and an obvious decreasing carrier concentration and Hall mobility. This may be due to the increase of grain boundary scattering resulting from the decrease in grain size and the segregation of dysprosium oxide at the grain boundaries. The resistivity of the deposited ZnO:(Dy) thin films decreased as the Dy2O3content increased

thank you so much sir for your valuable time and suggestion