Electromagnetic properties of multiphase composites containing barium strontium titanate and nickel zinc ferrite inclusions from 1-4 GHz

The growing importance of nonlinear transmission lines for pulsed power and high power microwave devices in defense and industrial applications motivates material development for system optimization. This study investigates composites manufactured with various volume loadings of both nonlinear magnetic (nickel zinc ferrite) and dielectric (barium strontium titanate) inclusions in a silicone matrix. Increasing the volume fraction of barium strontium titanate (BST) and nickel zinc ferrite (NZF) increased the permittivity with a stronger dependence on BST volume fraction. Increasing NZF volume fraction increased the magnetic permeability, while changing BST volume fraction had no effect. The DC dielectric breakdown voltage decreased exponentially with increased NZF volume fraction. Adding as little as 5% BST to an NZF composite more than doubled the breakdown threshold compared to a composite containing NZF alone. For example, adding 10% BST to a 15% NZF composite increased the breakdown strength by over 800%. The combination of tunability of permittivity and permeability by managing BST and NZF volume fractions with the increased dielectric breakdown strength by introducing BST make this a promising approach for designing high power nonlinear transmission lines with input pulses of hundreds of kilovolts.