Preface

A hot topic of research nowadays is the development and application of piezoelectric and thermoelectric materials. In addition to their direct application in energy harvesting, these materials are also being used to develop other high-added-value, multifunctional, and emerging applications. Either mechanical deformation or heat released environmentally by various processes can be utilized to generate electrical energy via the application of piezoelectric and/or thermoelectric materials.

This technical and scientific book compiles scientific research on some of the latest advances in piezoelectric and thermoelectric materials. The chapters within are organized into two sections. Section 1 includes five chapters that discuss piezoelectric materials, and Section 2 includes four chapters that discuss thermoelectric materials.

Chapter 1 introduces the characteristics and applications of two-dimensional materials, which are ideal materials for harvesting piezoelectric energy to be used in aerospace, military, automotive, and electronic clothing applications.

Chapter 2 examines the performance achieved by two-dimensional piezoelectric materials such as phosphorene, MXenes, Janus structures, heterostructured materials, and transition metal chalcogenides in energy harvesting for applications including self-powered sensors, self-powered devices, and regenerative actuators.

Chapter 3 investigates the use of time-resolved X-ray diffraction to study the amplified crystal lattice deformation and ionic displacements of resonant quartz crystals under an alternating electric field used in the implementation of piezoelectric oscillators for digital circuit applications.

Chapter 4 discusses the application of piezoelectric and magnetoelectric materials to take advantage of acoustic and mechanical vibrations, as well as magnetic fields produced by alternating current, to harvest energy.

Chapter 5 presents an equivalent circuit model of laminated magnetostrictive and/ or piezoelectric composite materials to predict their behavior under dynamic electromagnetic fields for both the direct and inverse effects in the longitudinal-transverse and transverse-transverse modes.

Chapter 6 evaluates different thermal conductivity models for thermoelectric materials both phenomenologically and analytically to identify the most convenient materials to develop high-temperature applications such as thermal barrier coatings.

Chapter 7 analyzes a quantum unit as a temperature standard to develop highprecision and high-efficiency thermoelectric applications using one- and twodimensional nanomaterials as well as nanostructured materials in energy harvesting. Chapter 8 discusses the reduced variables methodology using computational tools in the optimal design of thermocouple legs to determine different possible sets of suitable longitudinal dimensions in the same temperature range to produce electrical power on a load.

Finally, Chapter 9 reviews the applications of thermoelectric generators in health care for wearable applications to identify the resulting operational problems and those that remain to be resolved to offer a better quality of life for patients who require energy storage devices in sensors.

This book is a valuable source of information on piezoelectric and thermoelectric materials for undergraduate and graduate students, as well as professionals, experts, and researchers interested in this cutting-edge topic and high-added value applications. The editors appreciate all the time and effort made by the authors of the research presented in this book. Likewise, we are grateful to the IntechOpen staff, especially Ms. Tea Jurcic for her valuable support throughout the editing process. Finally, the senior editor would like to thank his wife, son, parents, brothers, and sisters for their help and support.

> **Dr. Rafael Vargas-Bernal** Department of Communications and Electronics Engineering, University of Guanajuato, Salamanca, Guanajuato, México

## **Dr. Roberto Palma Guerrero**

Section 1

Piezoelectric Materials

Department of Structural Mechanics and Hydraulic Engineering, University of Granada, Granada, Spain Section 1
