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 characterization 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...