Development of nanocrystalline Mn-Zn ferrites for high frequency transformer applications

Microwave-Hydrothermal (M-H) method has been successfully used for the synthesis of nanocrystalline Mn-Zn ferrites which are used for high-frequency applications. As synthesized powders were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanopowders were annealed at 600 degrees C/20 min using the microwave sintering method. The frequency dependence of dielectric constant (epsilon') was measured in the range of 10 Hz-1.3 GHz and initial permeability (mu(i)) was measured in the range of 10 Hz-1 MHz. The total power loss (P-t) was measured on the annealed samples at 100 kHz and 200 mT condition. Conductor-embedded-ferrite transformers were fabricated and output power (P-o), efficiency (eta) and temperature rise (Delta T) were measured at sinusoidal voltage of 25 V at 1 MHz. The transformer efficiency (Z) was found to be high and surface rise of temperature (Delta T) is very low. (C) 2009 Elsevier B.V. All rights reserved.