Influence of Non‐Stoichiometry on the Structure and Properties of Ba(Zn_1/3Nb_2/3)O₃ Microwave Dielectrics. IV. Tuning τ_f and the Part Size Dependence of Q×f

Abstract

High Q ceramics of Ba3W2O9 (BW)‐substituted Ba(Zn1/3Nb2/3) O3 (BZN) were prepared with a zero τf through the partial substitution of Zn by Ni and Co. The small concentrations of B‐site vacancies introduced by the substitution of BW accelerated the kinetics and stability of the cation ordering and lowered the sintering temperature. Dense, zero τf, ordered solid solutions such as 0.99Ba(Zn0.3Co0.7)1/3Nb2/3O3–0.01BW with ɛr=34.4 and Q×f=82 000 at ∼8 GHz could be obtained after sintering at 1380°C for 5 h and annealing at 1300°C for 24 h. Partially ordered ceramics in the Zn/Co and Zn/Ni solid solutions show a large gradient in the ordering throughout the pellets, which produces a resonant frequency dependence of their Q×f value. The ordering gradient is associated with the increased constraints on the growth of the 1:2 ordered structure within the interior of larger and thicker pellets and can be minimized by extended annealing.

Influence of Non‐Stoichiometry on the Structure and Properties of Ba(Zn1/3Nb2/3)O3 Microwave Dielectrics: III. Effect of the Muffling Environment

“…Other aspects of the ordering gradients, in particular, their impact on Q, will be discussed in a separate publication. 13 The different muffling environments also affect the structure and dielectric properties of the non-stoichiometric samples of BZN in the (1Àx) BZNÀ(x)BaNb 4/5 O 3 system. However, in contrast to stoichiometric BZN, excellent Q Â f values were obtained for the ZnO-vapor-protected samples as well as for those muffled in their own powder.…”

Effects of substrate on the crystalline structure and microwave dielectric properties of Bi1.5Mg1.0Nb1.5O7 sol–gel thin films

“…The XRD and SEM measurements exhibit that the crystallinity increases gradually in the films deposited on the glass, the ceramic and the Si(1 0 0). Secondly, It is demonstrated that cubic pyrochlore structure with preferred (2 2 2) orientation is regarded to be a positive factor for large dielectric constant [7,[44][45][46]. The XRD results reveal that the film on Si(1 0 0) substrate shows strong (2 2 2)-oriented texture, and that of the glass and ceramic substrate samples exhibit slightly (2 2 2) and (4 0 0) orientations, respectively.…”