In this paper, we report the multiferroic and piezoelectric behavior observed in transition-metal doped ZnO films. The experimental results indicated that the Co-doped ZnO films deposited by magnetron sputtering possess a Curie temperature higher than 700K, and the magnetic moments of Co are intimatedly correlated to the doping concentration and the substrate. A giant magnetic moment of 6.1 B/Co is observed in (4 at.%) Co-doped ZnO films. Ferroelectric and ferromagnetic behaviors simultaneously were also obtained in V and Cr doped ZnO films on Pt(111)/Ti/SiO2/Si(100) substrates by reactive sputtering method, revealing a multiferroic nature. The high piezoelectric d33 coefficient 80-120 pm/V has also been achieved by Cr and V substitutions, which could make Cr-doped or V-doped ZnO a promising material in piezoelectric devices.

As a member of Electroactive Polymers (EAPs), dielectric elastomer (DE) has shown considerable potential for energy harvesting applications. After the basic principle of DE energy harvesting is studied, a multi-layer DE generator using VHB 4910 (3M, USA) is specially designed and fabricated. Then, an improved energy harvesting circuit is designed to make use of harvested electrical energy. Finally, energy harvesting experiments are implemented under the constant charge (open-circuit) condition and the results prove that the multi-layer DE generator fabricated can produce enough energy to constantly drive a light emitting diode. The harvested electrical energy has good consistent with generated electrical energy and the maximum energy harvesting efficiency ηh can reach 89%.