Influence of Non‐Stoichiometry on the Structure and Properties of Ba(Zn _1/3 Nb _2/3 )O ₃ Microwave Dielectrics: III. Effect of the Muffling Environment

The effect of different muffling environments on the structure and dielectric losses of Ba(Zn _1/3 Nb _2/3 )O ₃ (BZN) microwave ceramics was investigated. The microwave dielectric losses of stoichiometric BZN pellets heated in ZnO‐rich environments were severely degraded (e.g. Q × f ∼15 000 in ZnO powder) compared with samples muffled in their own powder ( Q × f ∼80 000). Structure analyses and gravimetric measurements confirmed that the ceramics muffled in ZnO powder or vapor absorb excess ZnO to form non‐stoichiometric solid solutions with reduced cation order and Q . By using starting compositions in the (1− x )BZN−( x )BaNb _4/5 O ₃ binary ( x =0.04), the stoichiometry can be tailored to ensure that after the uptake of ZnO, the ceramics remain well ordered and are located in a high Q region of the system. For example, ZnO‐vapor‐protected (0.96)BZN−(0.04)BaNb _4/5 O ₃ reached a very high Q × f (∼1 05 000) after sintering at 1400°C for 5 h.