Xubai Zhang

Static and high frequency magnetic and dielectric properties of ferrite-ferroelectric composite materials

A series of sintered composite materials was fabricated from Parascan™ barium strontium titanate (BSTO) and Trans-Tech nickel zinc ferrite powders. The ferrite loading was varied from zero (BSTO only) to 100wt% (ferrite only). X-ray diffraction data show the presence of a third, nonmagnetic phase that sets the ferrite loading at values somewhat lower than the as prepared wt % amounts. The average magnetization is found to scale linearly with the loading. The initial susceptibility, saturation field, and coercive force as obtained from hysteresis loop data show trends consistent with these data. Ferromagnetic resonance linewidth and effective linewidth measurements at 10GHz show reasonable values for the 100wt% samples, but any amount of BSTO causes a severe degradation in both loss parameters. Similarly, it is found that any amount of ferrite causes a rapid drop in the relative dielectric constant that is consistent with standard mixing models. Loss tangent measurements gave modest values in the 0.001–0.0...

S-Band Microwave Phase Shifters Based on Ferroelectric Varactors

The S-band microwave (MW) phase shifters with different constructions based on BSTO ferroelectric varactors were investigated. Phase shifters were experimentally tested and the results are presented in this report.

Ferroelectric lens phased array antenna with interdigitated electrodes

Abstract The ferroelectric lens is a new type of phased array antenna. It uniquely incorporates bulk phase shifting using ferroelectric material to reduce the cost of the phased array. The array does not contain an individual phase shifter at each radiating element. So far, the work performed to develop the ferroelectric lens has included thick bulk ferroelectric material, which requires bias voltage of over 10 kV to provide 360° phase shift. This paper presents the results of a recent effort in developing a small column of the lens that uses much thinner material with interdigitated electrodes. This technique will reduce the bias voltage requirements for the ferroelectric lens. A brief review of the ferroelectric lens concept is also included.

Investigation of the effects of milling ceramic targets on the optical and electrical properties of BST thin films deposited by RF sputtering

Abstract The RF sputtering method was utilized to deposit thin films of Ba1-xSrxTiO3 (BST). The targets utilized in these experiments were prepared from ceramic powders with different particle size. The goal of this work is to examine whether the particle size distribution of the target can affect the properties of the thin films fabricated by the sputtering method. The Atomic Force Microscope (AFM) was used to examine the grain size in the thin films. The composition of the thin films and the bulk materials were examined by Fourier Transform Infrared (FTIR) spectroscopy. The dielectric properties of the thin films were measured and compared to its bulk counterparts. It was found that on lattice matched electrodes of SrRuO3 on LaAlO3 substrates, the thin films deposited from ceramic targets manufactured from ball-milled powders had finer grain size than those deposited from targets made from unmilled powders. However, this phenomenon was not observed in the case of polycrystalline films deposited on plati...