Magnetoelectric effects and power conversion efficiencies in gyrators with compositionally-graded ferrites and piezoelectrics

Low-frequency/resonance magnetoelectric interactions and power conversion efficiency of magnetoelectric gyrators consisting of compositionally-graded nickel zinc ferrites and lead zirconate titanate with a coil wound around it were proposed and systematically characterized. Grading-induced differences of magnetic moment and remnant magnetization in ferrites with composition of Ni1−xZnxFe2O4 (0 ≤ x ≤ 0.3) can create the desired built-in field to decrease the required bias. The samples were characterized in terms of magnetostriction, low-frequency/resonance and power conversion efficiency with varieties of Zn concentrations, reversal sequence and volume ratio. A maximum PE of 62.9% was achieved in the composite of PZT-NiFe2O4-Ni0.9Zn0.1Fe2O4 at H = 10 Oe with volume ratio n = 0.5 under load RL = 700 Ω. With contribution of the desired built-in field, maximum PE of 60% under zero bias was also achieved in similar conditions. These favorable features open up the possibilities of ME gyrators with grading for promising applications in power electronics, converters and wireless energy harvesters without a sacrifice in device volume and modest rise in magnetomechanical efficiency.