Magnetically Induced Carrier Distribution in a Composite Rod of Piezoelectric Semiconductors and Piezomagnetics

Shear horizontal waves in a multiferroic composite semiconductor structure

Piezoelectric semiconductors (PSs) possess the physical properties of piezoelectric and semiconductor simultaneously. When a piezomagnetic (PM) material is added to the PS, the composite structures will exhibit the comprehensive mageto-electro-semiconductive (MES) coupling effects. In this paper, the propagation characteristics of shear horizontal (SH) waves in a multiferroic composite semiconductor structure are investigated, where a n-type PS thin plate is perfectly bonded to a semi-infinite PM substrate. Based on the three-dimensional macroscopic theory for PS and PM, the dispersion equations are derived analytically. Numerical examples are presented to study the effects of steady-state carrier density, cover thickness, and material properties on the phasevelocity and attenuation of SH wave systematically. The developments of various electromechanical fields through the thickness of the layers are discussed. The results show that initial electron concentration (n0) has an important effect on the distribution of most physical quantities such as displacement, stress, electric potential and electric polarization, but magnetic potential and magnetic flux density are insensitive to n0. The piezoelectric constant e15 and piezomagnetic constant f15 have different effects on the SH wave propagation and magnetic potential distribution. The theoretical results could be helpful for the analysis and design of PS-PM structures or related surface acoustic wave (SAW) devices.

Theoretical Analysis of Piezoelectric Semiconductor Thick Plates with Periodic Boundary Conditions

Piezoelectric semiconductors, being materials with both piezoelectric and semiconducting properties, are of particular interest for use in multi-functional devices and naturally result in multi-physics analysis. This study provides analytical solutions for thick piezoelectric semiconductor plates with periodic boundary conditions and includes an investigation of electromechanical coupling effects. Using the linearization of the drift-diffusion equations for both electrons and holes for small carrier concentration perturbations, the governing equations are solved by the extended Stroh formalism, which is a method for solving the eigenvalues and eigenvectors of a problem. The solution, obtained in the form of a series expansion with an unknown coefficient, is solved by matching Fourier series expansions of the boundary conditions. The distributions of electromechanical fields and the concentrations of electrons and holes under four-point bending and three-point bending loads are calculated theoretically. The effects of changing the period length and steady-state carrier concentrations are covered in the discussion, which also reflects the extent of coupling in multi-physics interactions. The results provide a theoretical method for understanding and designing with piezoelectric semiconductor materials.

Bending Analysis of Multiferroic Semiconductor Composite Beam towards Smart Cement-Based Materials

A beam-like structure of antisymmetric laminated multiferroic piezoelectric semiconductor (LMPS), which consists of two piezomagnetic (PM) and two piezoelectric semiconductor (PS) layers is proposed. The structure could be in pure flexure deformation under an applied magnetic field. Through this deformation mode and the induced polarization field through the magneto-electro-semiconductive (MES) coupling mechanism, the semiconducting properties of PS layers can be manipulated by the applied magnetic field. In order to better understand and quantitatively describe this deformation mode, the one-dimensional governing equations for the LMPS beam are developed based on the three-dimensional theory. The analytical solutions are then presented for the LMPS cantilever beam with open-circuit conditions. The multi-field coupling responses of the LMPS cantilever beam under the longitudinal magnetic field are investigated. Numerical results show that the amplitude of each physical quantity is proportional to the applied magnetic field, and the thickness ratio of the PS phase plays a significant role in the MES coupling behaviors of the LMPS beam. The proposed structure can be integrated into cement structures but also fabricated cement-based multiferroic PS composite materials and structures. It provides an important material and structure basis for developing structural health monitoring systems in the fields of civil and transportation infrastructures.

Smart Materials

The future of engineering systems is based on the capability of integrating sensors, actuators, control systems and materials [...].