The present book encompasses and gives brief information about pyrophosphate materials. It also explains their phenomenological theories and properties of rare-earth activated pyrophosphates. This book provides the comprehensive in depth information about the development of phosphates and pyrophosphates along with their essential characterisation techniques as well as their diversified applications in numerous domains. This book envelopes all essential information about single and mixed cations pyrophosphate compounds that have been used in past few years. It also covers intact information about innovation in advance pyrophosphate materials especially for their applications in medicinal field. In particular, this book focuses on enhanced chemical and physical properties of pyrophosphate as there is a need for new low-cost, less toxic and energy efficient materials to reduce the current cost of device technologies. This book masterfully demonstrates the present scenario of pyrophosphates and concurrent technologies with its increasing significance to resolve energy- and environment-related problems and their sustainable approach in the world of globalisation.