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

Objectives - Fabrication of Ni-Zn high permeability ferrites. - Synthesis of BST compositions. -Composites with  =  = at 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 /2; the necessary length of a dipole of an antenna.

Why permeability and permittivity In the composite, the wave length for electromagnetic waves is reduced by a factor of index of refraction n = (  r  r ) 1/2 For  = , one also has impedance matching with free space, a necessary condition for efficient energy transfer: Z=Z o (μ r /ε r ) 1/2 Therefore, if  = , then Z = Z o

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

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 –  = 

Composite synthesis 1.Calculating Stoichiometric ratios for the composites. 2. Mixing the powders, adding the correct weight of each. Powders Used NiOZnOFe CoCo 3 MnO Ni x Zn 1-x Fe X= 0.2 and %NZFO/5%BST

Composite Synthesis Cont. 3.Ball Milling the powders. (Adding Methanol) 4.Pre-sinter the powders at 650 o C. BALL MILLING

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

Ni-Zn Ferrites Ni 1-x Zn x Fe 2 O 4 (NZFO)  increases with x Permeability Spectra (x=0.2)  decreases and loss increases above 10 MHz!

Substitutions in Ni-Zn ferrites 10 mole% of Co: (Ni 0.7 Zn 0.2 Co 0.1 Fe 2 O 4 )  decreases, but stays constant up to 500 MHz! 95% NZFO (x-0.2) – 5% PZT Work in progress!  = for MHz

Results Efforts to-date have resulted in  =  =10-30 for MHz range. We plan to : (i)increase the permeability with higher amount of Zn in the ferrite, (ii)enhance the frequency band-width cobalt substitution in the ferrite, and (iii) achieve  =  by tailoring the composite composition.