Publication Date:
2017-09-21
Description:
Domain engineering via oxygen vacancy, V O •• , loading achieved by A/B modification as well as quenching treatment, was utilized for Ba 0.8 Sr 0.2 TiO 3 (0.8 BSTs) in an attempt to enhance the microwave tunable characteristics. For similar grain sizes, the domain sizes were notably reduced for all non-stoichiometric BSTs, indicating that the loaded V O •• (as a consequence of Ti defects, V Ti ′′′′ ) played a role in the nuclei for new domain walls. The tunability T at 100 MHz under a direct current field of 30 V/20 μm increased steadily as the domain size ( d.s .) declined for all BSTs, regardless of the A/B ratio, due to the d.s . effect. The tunable characteristics in non-stoichiometric BSTs having a similar d.s . of ˜ 190 nm were then compared. The tunability and tan δ decreased for A/B = 1.002 (0.2 mol% Ti defects). The introduced V O •• formed pinning centers that restricted domain wall motion, leading directly to lower tunability and smaller dielectric loss. However, V O •• -overloaded samples (i.e., A/B ≥ 1.005) exhibited increased values for tan δ due to V O •• conduction in the domains. The quench treatment of 0.8 BST (with A/B = 1.002) samples resulted in a d.s . reduction from 191 to 170 nm. These quenched specimens showed greater tunability, T total , originating from the strengthened dipole contribution, T dipole , as a consequence of the d.s . effect. The tan δ of the quenched specimens was essentially unchanged, indicating a homogenous V O •• distribution via the quench, effectively reducing the mobile V O •• (which contributes to electrical conduction) in the domains. Consequently, the achieved figure of merit via domain engineering was 2.25 at 100 MHz for the quenched BST with A/B = 1.002, which was 1.54 times larger than that of unmodified BST. This article is protected by copyright. All rights reserved.
Print ISSN:
0002-7820
Electronic ISSN:
1551-2916
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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