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

Abstract

Polycrystalline neodymium‐doped yttrium aluminum garnet (YAG), Nd: Y3Al5O12, 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.

Ceramic Laser Materials

“…Similar results have been observed by others and are listed in Table 4 and can be attributed to the increased fracture toughness of the ceramic [14,15,16]. …”

Densification of transparent yttrium aluminum garnet (YAG) by SPS processing

“…Excess Li released from the additive is incorporated in the ceramic YAG matrix, substitutes for the higher positive valence Y and/or Al cations and, as a result of charge equilibrium requirements, generates oxygen vacancies as shown, using the Kroger-Vink notation, in Eqs. (1) and (2):…”

“…It displays excellent high temperature strength and low creep rate and reasonably good mechanical properties. 1 It is well known as a laser gain host crystal and as an excellent IR transparent window material. Initially, YAG was utilized essentially in its single crystal form, over the last decades, however, due to the greatly enhanced availability of high purity powder and advanced processing technologies, polycrystalline YAG has also been manufactured at required quality levels.…”

Nd:YAG transparent ceramics fabricated by direct cold isostatic pressing and vacuum sintering

“…Among these rare-earth ions, Nd 3+ isthemost common optically active element dopant [12][13][14][15][16]. For a long time, it was considered the Nd:YAG single crystal conventionally grown by the Czochralski method to be excellent laser host material, although it has several limitations [17][18][19]. In recent years, Nd:YAG ceramics have attracted much attention owing to their flexible structural designing and excellent laser properties.…”