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Slow Wave Materials for Highly Efficient Miniaturized Antennas with Enhanced band-width

Slow Wave Materials for Highly Efficient Miniaturized Antennas with Enhanced band-width. David Elliott. Objectives. - Fabrication of Ni-Zn high permeability ferrites. - Synthesis of BST compositions. Composites with m = e = 50-100 at 10-100 MHz.

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Slow Wave Materials for Highly Efficient Miniaturized Antennas with Enhanced band-width

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  1. Slow Wave Materials for Highly Efficient Miniaturized Antennas with Enhanced band-width David Elliott

  2. Objectives - Fabrication of Ni-Zn high permeability ferrites. - Synthesis of BST compositions. • Composites with m = e = 50-100 at 10-100 MHz. • Used to create a slow wave material that will allow for miniaturization of antennas. This is done by slowing the wave down, lowering the size of l/2; the necessary length of a dipole of an antenna.

  3. Why permeability and permittivity • In the composite, the wave length for electromagnetic waves is reduced by a factor of index of refraction n = (er mr)1/2 • For m=e, one also has impedance matching with free space, a necessary condition for efficient energy transfer: Z=Zo (μr/εr)1/2 Therefore, if m=e, then Z = Zo

  4. Materials Approach Ni-Zn Ferrites/BST BST has a composition of 60% Barium Titanate / 40%Strontium Titanate

  5. What are Ferrites? - Oxides with Fe, Co, Ni .. And other divalent or trivalent ions. • Magnetically ordered at room temp. • High permeability and low loss at microwave frequencies. What is BST? Barium Strontium Titanate (Ferroelectric) High permittivity Ferrite/BST – right proportion – m = e

  6. Composite synthesis 1.Calculating Stoichiometric ratios for the composites. 2. Mixing the powders, adding the correct weight of each. NixZn1-xFe204 X= 0.2 and 0.3 95%NZFO/5%BST Powders Used NiO ZnO Fe203 CoCo3 MnO

  7. Composite Synthesis Cont. BALL MILLING 3.Ball Milling the powders. (Adding Methanol) 4.Pre-sinter the powders at 650oC. www.ilpi.com

  8. 5. Manual Pressing 6. Hot Pressing (1000oC-1050oC at 1250psi) 3-4 hours 7. Cut Sample 8. Annealing Sample (850oC-1200oC) 24 –72 hours Composite Synthesis Cont.

  9. Ni-Zn Ferrites Ni1-x Znx Fe2O4 (NZFO) m increases with x Permeability Spectra (x=0.2) m decreases and loss increases above 10 MHz!

  10. Substitutions in Ni-Zn ferrites 10 mole% of Co: (Ni0.7Zn0.2Co0.1Fe2O4) m decreases, but stays constant up to 500 MHz! 95% NZFO (x-0.2) – 5% PZT Work in progress! m = 50-100 for 10-100 MHz

  11. Results Efforts to-date have resulted in m=e=10-30 for 10-100 MHz range. We plan to : • increase the permeability with higher amount of Zn in the ferrite, • enhance the frequency band-width cobalt substitution in the ferrite, and • achieve m=e by tailoring the composite composition.

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