Lectures on Termodynamics and Phase Diagrams

Abstract

This book is the result of several years of teaching of the Faculty of Science in physical engineering and optoelectronics at the Autonomous University of San Luis Potosi (UASLP). It is devoted to the essential, in my opinion, area of material science and technology: thermodynamics related to various phase diagrams. I realized that there was a lack of appropriate literature that would clearly and thoroughly explain the necessary topics for students. I have tried to present the material simple, and accessible to students of different levels of education. Thus, to understand it, you only need to be familiar with the concepts of differential and integral calculus. The book consists of six chapters. The first and second chapters are concerned with the basic concepts of thermodynamics, that are used in the construction and analysis of various phase diagrams: the first law of thermodynamics, the equation and function of state, thermodynamic work, properties of the ideal gas and the Carnot cycle. The second law of thermodynamics is outlined on the basis of these essentials and the concept of entropy is introduced. These two chapters, although they review basic concepts in classical thermodynamics, have been included in the text after some hesitation to make the subsequent sections of the book clearer and to produce a more complete and self- contained work. An attentive reader familiar with the basic concepts of thermodynamics will be able to skip this part, aimed especially for beginning students, without compromising their understanding. In the third chapter, thermodynamic functions such as internal energy, enthalpy or heat, Gibbs and Helmholtz energies are studied. The fundamental Gibbs equation and the general conditions for thermodynamic equilibrium in any complex system are also discussed here. On the basis of these conditions, in chapters four, five, and six the phase diagrams of various systems are discussed, starting with the one-component system and continuing with the two-component, three-component, and multicomponent systems. Here I discuss in detail the state diagram for A3B5 systems and solid solutions on their basis. These materials are used widely today to fabricate various optoelectronic devices such as laser diodes, LEDs, detectors, and photovoltaic converters. I analyze in detail the conditions of the solution decomposition in the regular model, as well as the state diagram of multicomponent systems and methods of experimental and theoretical study of these diagrams. Of course, a text like this could be continued and expanded. Subsequent editions may be supplemented by a presentation of nucleation theories and models, and details of crystal growth theory (Czochralski, Bridgman, fusion zone), as well as descriptions of such technologies as liquid, gas, and molecular epitaxy.