Printable Nanocomposites with Superparamagnetic Maghemite (γ‐Fe ₂ O ₃ ) Particles for Microinductor‐Core Applications

Abstract Reducing losses in inductor core materials allows further miniaturization and increase of efficiency in power converters. Nanocomposites containing superparamagnetic 11 3 nm ‐ 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 ‐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 ‐field amplitude of 30 mT, commonly used in inductor core materials for power electronics, the losses are on the order of – kW . 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.