Comparison of the Mechanical Properties of Single Crystal and Polycrystalline Yttrium Aluminum Garnet

Polycrystalline neodymium‐doped yttrium aluminum garnet (YAG), Nd: Y ₃ Al ₅ O ₁₂ , has been produced in a transparent form and is being considered as a substitute for single crystal YAG in laser applications. To determine whether such a substitution could impact mechanical reliability, it is critical to compare the baseline mechanical properties of the single crystal and polycrystalline materials. In this study, elastic constants, hardness, fracture toughness and strength properties were measured using standard experimental procedures. In addition, fractography was used to gain insight into the fracture process and the nature of the flaws controlling the strength behavior. Overall, it was determined that the mechanical behavior of the polycrystalline YAG was very similar to that of the single crystal material. The elastic constants of polycrystalline YAG were almost the same as the single crystal and the polycrystalline material showed slight advantages in hardness and fracture toughness. Surface machining flaws were found to control the strength behavior with the single crystal material being the more sensitive to contact damage and, hence exhibiting a lower strength.