Anomalous Correlation between Dielectric Constant and Tunability in (Ba,Sr)TiO₃–MgO–Mg₂SiO₄ Composite Ceramics

Abstract

(Ba, Sr)TiO3–MgO–Mg2SiO4 composite ceramics were prepared by a solid‐state reaction method. The microstructures, microwave dielectric characteristics, and tunability of composite ceramics were investigated. An anomalous correlation between tunability and dielectric constant was observed: with the increase in Mg2SiO4 content and the decrease in MgO content, the dielectric constant of (Ba, Sr)TiO3–MgO–Mg2SiO4 composite ceramics decreases, but the tunability increases. The anomalous increased tunability is beneficial for tunable microwave applications and can be attributed to the redistribution of the electric field. For 50Ba0.5Sr0.5TiO3–(50−x)MgO–xMg2SiO4, the dielectric constant was decreased from 164.2 to 126.5 by increasing Mg2SiO4 content from 5 to 45 wt% and the tunability at 3.9 kV/mm increased from 11.5% to 15.2%.

The Impact of Composite Effect on Dielectric Constant and Tunability in Ferroelectric–Dielectric System

“…In our recent work, with the increase in Mg 2 TiO 4 from 7.5 to 50 wt%, the tunability of Ba 0.45 Sr 0.55 TiO 3 –Mg 2 TiO 4 and Ba 0.5 Sr 0.5 TiO 3 –Mg 2 TiO 4 under 2 kV/mm increased from 4.3% to 9.7% and from 8% to 14.2%, respectively . This unusual increased tunability can also be observed in the Ba 0.5 Sr 0.5 TiO 3 –Mg 2 SiO 4 –MgO and BST‐MgO system …”

“…12 This unusual increased tunability can also be observed in the Ba 0.5 Sr 0.5 TiO 3 -Mg 2 SiO 4 -MgO and BST-MgO system. 6,10 Sherman et al have theoretically studied the dielectric properties of ferroelectric-dielectric composites. 16 In the spherical inclusion model, with a series of simplification, a formula which can describe the tunability was determined to be: n r = n f (1 + 0.2q).…”

“…However, some ferroelectric materials, such as (Ba, Sr)TiO 3 , with high dielectric constant and inherent material loss, have restricted their application in the field of tunable microwave devices. Generally, adding linear dielectrics with low dielectric constant into these ferroelectrics is an effective method to decrease their dielectric constant and loss and keep the tunability at a sufficiently high level . Therefore, the study of how linear dielectric content impact the dielectric properties in the ferroelectric–dielectric system is meaningful.…”

“…Generally, adding linear dielectrics with low dielectric constant into these ferroelectrics is an effective method to decrease their dielectric constant and loss and keep the tunability at a sufficiently high level. [6][7][8][9][10] Therefore, the study of how linear dielectric content impact the dielectric properties in the ferroelectric-dielectric system is meaningful.…”

The anomalous increase in tunability in Ba0.55Sr0.45TiO3‐MgO‐Mg2SiO4 composite ceramics

“…More recently, we observed that the abnormal increase in tunability also emerged in Ba 0.45 Sr 0.55 TiO 3 –MgO–Mg 2 TiO 4 system, which supports our speculation. We have investigated the dielectric tunable properties of BST–Mg 2 SiO 4 –MgO composite ceramics previously . Fixing dielectric content unchanged, with the increase in Mg 2 SiO 4 content and the decrease in MgO content, the tunability of composites increases.…”