Skip navigation, view page content
Summer 2008 Seminar
Friday, July 25, at 3:30 p.m. room 184 Watts Hall
Lanlin Zhang
PhD Candidate advised by Dr. Henk Verweij
Department of Materials Science and Engineering
The Ohio State University
Fabrication and materials of magneto-photonic assemblies for high-gain antenna applications at GHz frequencies
Abstract
Recent magnetic photonic assemblies (MPAs) designed for high-gain antennas require low-loss, strongly anisotropic dielectrics and ferrimagnetic materials. Artificial anisotropic dielectrics (AD) are fabricated from laminates, which consist of two ceramics with largely different permittivities and low dielectric losses at GHz frequencies. High gain has been demonstrated in a prototype antenna with 6 misaligned AD layers laminated from commercially available α-Al2O3 and Nd-doped BaTiO3. Equivalent permittivity tensors and loss tangents (tan δ˜1.9x10-3) were characterized using a resonant cavity based approach, coupled with a finite-element method full-wave solver. To minimize tan δ, dense high-purity α-Al2O3 and TiO2 were prepared starting from colloidally stabilizing the powders in HNO3 and NH3 solutions respectively.
After colloidal filtration and sintering, α-Al2O3 with >99.0% density was achieved at a low sintering temperature of 1300°C, and TiO2 with >99.5% density obtained at 1000°C, due to excellent compact homogeneity. TiO2 was observed with a low tan δ of 1.4x10-4 at 6.4 GHz at room temperature, attributed to the homogeneous dense microstructure with 2.2µm grain size. Al3+ was doped into TiO2 using a modified impregnation method to compensate reduction of Ti4+. A homogeneous microstructure and doping concentration was observed in the doped dense TiO2. Substituted Y3Fe5O12 garnet was chosen as the ferrimagnetic component, due to its potential low magnetic and dielectric loss. Phase pure garnet was prepared using citric-gel method. The magnetic properties were studies for different substitution compositions and as-prepared particle morphology. An Al, In substitute garnet with submicron particles was observed with low loss at GHz range, and will be applied in the MPAs structure.
Bio
Lanlin Zhang received her B.S. in Materials Science from Fudan University (Shanghai, China) in 2003. She has been working towards her Ph.D. in Materials Science and Engineering under the guidance of Dr. Hendrik Verweij since 2003.
