Printable Nanocomposites with Superparamagnetic Maghemite (γ-Fe2O3) Particles for Microinductor-Core Applications

Reducing losses in inductor core materials allows further miniaturization and increase of efficiency in power converters. Nanocomposites containing superparamagnetic 11 (Formula presented.) 3 nm (Formula presented.) - (Formula presented.) particles in a polyvinyl alcohol polymer matrix were developed as printable and castable inductor core materials for MHz range frequencies. The aqueous synthesis resulted in nanocomposites of well-dispersed particles with volume fractions ranging from 10% to 45%. The nanocomposite is eddy current free, has high volume susceptibility up to 17, and a constant AC response in the Hz–kHz range. Hysteresis measurements at 100–900 kHz show that power losses scale as (Formula presented.) -field squared and with frequency to the power of 1–1.3, indicating that the only loss mechanism is high-frequency hysteresis. For an induced (Formula presented.) -field amplitude of 30 mT, commonly used in inductor core materials for power electronics, the losses are on the order of (Formula presented.) – (Formula presented.) kW (Formula presented.). These losses can be reduced by using more monodisperse particles. The presented nanocomposite is easily integrated into micro-fabrication methods, demonstrated by depositing nanocomposite cores on printed circuit board inductors. The inductors with nanocomposite core, measured up to 100 MHz, display an increase in inductance compared to air-core inductors. This showcases superparamagnetic nanocomposites as relevant candidates for high-frequency applications such as portable electronics.