Improvement of dielectric tunability and loss tangent of (Ba,Sr)TiO₃thin films with K doping

Abstract

Ba0.6Sr0.4TiO3 thin films doped with K were deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method. The structure, surface morphology and the dielectric and tunable properties of Ba0.6Sr0.4TiO3 thin films have been studied in detail. The K content in Ba0.6Sr0.4TiO3 thin films has a strong influence on the material's properties including surface morphology and the dielectric and tunable properties. It was found that the Curie temperature of K-doped Ba0.6Sr0.4TiO3 films shifts to a higher value compared with that of undoped Ba0.6Sr0.4TiO3 thin films, which leads to a dielectric enhancement of K-doped Ba0.6Sr0.4TiO3 films at room temperature. At the optimized content of 0.02 mol, the dielectric loss tangent is reduced significantly from 0.057 to 0.020. Meanwhile, the tunability is enhanced obviously from 26% to 48% at the measured frequency of 1 MHz and the maximum value of the figure of merit is 23.8. This suggests that such films have potential applications for tunable devices.

Ultrahigh frequency tunability of aperture-coupled microstrip antenna via electric-field tunable BST

“…[4] BST also shows great prospective in some tunable microwave components, such as phase shifter, [5] tunable filter, [6] varactor, [7] delay line, [8] etc. Comparing with bulk BST, the BST film possesses a superior tunability and lower relative permittivity (ε r = 300-800), [6,9] however, the preparation methods, such as pulsed laser deposition, magnetron sputtering and metalorganic chemical vapor deposition, are too expensive to be used in the microwave industry. [10][11][12] In this study, low cost BST composite ceramics are prepared by solid state reaction process for fabricating FRC antennas.…”

The low-temperature sintering and microwave dielectric properties of (Zn0.7Mg0.3)TiO3ceramics with H3BO3

“…Hence, the decrease in sintering temperature is a key problem in the application of LTCCs in the fabrication of dielectric devices such as resonators, filters, and duplexers. [4,5] Zinc titanate (ZnTiO 3 )-based systems exhibit good microwave dielectric properties of a high dielectric constant (∼ 20) and good quality factor (Q × f = 33000 GHz), and τ f ≈ −55 ppm/ • C. [6][7][8] Therefore, ZnTiO 3 ceramics have been developed and used as microwave materials for LTCCs. [9][10][11] However, there are some difficulties in obtaining singlephase hexagonal ZnTiO 3 .…”