Correlation between the 1:2 atomic order and microwave dielectric loss in the off-stoichiometric Ba(Zn1/3Ta2/3)O3

We report close correlation between the 1:2 atomic order and microwave dielectric loss in the off-stoichiometric Ba(Zn1/3Ta2/3)O3 (BZT). Small off-stoichiometric deviations have a large effect on the ordering and Q × f values. The Ba4Ta2O9-BZT-'Zn4Ta2O9' pseudo tie line separating the Ta-rich and Ta-poor regions also demarcates the 1:2 ordered and disordered BZT. The low-loss off-stoichiometric BZT ceramics are located in the 1:2 ordered region of the BaO-ZnO-Ta2O5 phase diagram. Without exception the disordered BZT ceramics show high dielectric loss. Stoichiometric BZT with 1:2 atomic order shows Q × f = 113 THz. The off-stoichiometric 1:2 ordered BZT ceramics with the highest Q × f > 200 THz are located in the ZnO-deficient part of the ternary phase diagram.