Masters Thesis

Multiferroic motor design, fabrication, and characterization

The proposed research is a scientific feasibility and characterization study of a multiferroic motor stator constructed of two rings. An outer piezoelectric ring (e.g., lead zirconate titanate) was concentrically bonded to an inner magnetostrictive ring (e.g., Terfenol-D). The objective of the study was to determine if a specific macroscale multiferroic design could operate as a motor stator and thus be considered as an alternative to traditional electromagnetic motors. The motivation for the macroscale design stemmed from nanoscale multiferroic designs which have proven to be advantageous in efficiency and power density. An experimental setup was created, in which a bias magnetic field was applied to the bulk motor structure, i.e. composite multiferroic ring structure, and an AC electric field was applied to the piezoelectric ring. The bias magnetic field was monitored using a Gaussmeter, while the electric field was measured using a high-voltage probe and was observed on a digital oscilloscope. The generated AC magnetic field was measured using search coils and a Lock-In amplifier. The bias magnetic field ranged between 0 and 2000 Oe, while the applied electric field was varied between 0 and 400 volts. The frequency of the AC electric field ranged between 4 and 45 kHz. The resonant frequency was found to be 36 kHz. It was found that the investigated motor design did not generate a rotating magnetic field indicating that this design is not feasible as a stator. This was attributed to the lack of change in magnetization of the inner Terfenol-D ring upon the application of the electric field to the piezoelectric outer ring. Additionally, a dependence of the magnetization on the applied voltage was observed. However, the effect was equal for the tested voltages ranging from 100Vpp to 400Vpp. The converse magnetoelectric (CME) coefficient was found to be near 5 mG/V for non-resonant frequencies with a drastic increase to 100 mG/V at resonance (36 kHz). Data indicate that the design may be suitable for sensor application or use as an RF magnetic field generator for nano/micro resonators.

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