The MATERIALS IN ACTION series has been produced by the Materials Engineering Department of the Open University's Technology Faculty as an undergraduate-level text. Its publication in book format brings the Open University's highly regarded texts and teaching methods to a wider audience. The series comprises four books: Materials Principles and Practice Manufacturing with Materials Structural Materials Electronic Materials Each book is self-contained and is based on an industrial context. Electronic Materials is about materials that are used for their electrical and magnetic properties, rather than their mechanical properties. Exploiting electronic properties in many products calls for careful manipulation of materials' structures at the atomic and microstructural levels. The book explains the scientific models needed to guide those manipulations and describes how they are commercially exploited inside electronic devices. Printed, hybrid and integrated circuit technologies are discussed together with ways of providing circuit components at each scale. Electronic and magnetic transducers, magnetic components (such as transformer cores and memory systems), optoelectronics, visual-display technologies and semiconductor memory systems are examined. A study of the interplay among the development, manufacture and marketing of innovative high-temperature superconductors puts these topics into an entrepreneurial context.