The Q*_f values of the Li2ZnTi3O8 ceramics as a function of the Bi2O3 addition and sintering temperature are shown in Fig. 4(b). The Q*_f value variation revealed similar tendency with the density of the Li2ZnTi3O8 ceramics .The microwave dielectric loss is caused not only by the lattice vibrational modes , but also by the density ,oxygen vacancies ,second phases, grain sizes, etc .[11].Larger grain resulted in less grain boundary which meant less lattice mismatch and lower dielectric loss.When Bi3+ ions substitute for Zn2+ sites of Li2ZnTi3O8 ceramics, the electrons are generated by the following equation: