In recent years, particular attention has been devoted to developing "soft" chemistry approaches towards the synthesis of new lanthanide (rare-earth) materials under ambient conditions. This book presents a simple hydrothermal synthetic approach to produce a number of new erbium-based materials in the form of crystalline microflowers, hexagonal microlayers, microsticks and microspheres, which are comprised of nanoparticles, as well as nanofibers, nanorods and nanolayers. This book also discusses recent results concerning the synthesis, phases changes and vibrational spectra of rare-earth orthophosphates, together with similar data for the diphosphate, ErKP2O7.2H2O, and the tricyclophosphate, ErNa3(P3O9)2.9H2O.