Abstract
Cubic rare-earth sesquioxide crystals are strongly demanded host materials for high power lasers, but due to their high melting points investigations on their thermodynamics and the growth of large-size crystals of high optical quality remain a challenge. Detailed thermal investigations of the ternary system Lu2O3–Sc2O3–Y2O3 revealing a large range of compositions with melting temperatures below 2200°C and a minimum of 2053°C for the composition (Sc0.45Y0.55)2O3 are presented. These reduced temperatures enable for the first time the growth of high optical quality mixed sesquioxide crystals with disordered structure by the conventional Czochralski method from iridium crucibles. An (Er0.07Sc0.50Y0.43)2O3 crystal is successfully grown and characterized with respect to its crystallographic properties as well as its composition, thermal conductivity and optical absorption in the 1 µm range.
Highlights
Cubic rare-earth sesquioxide crystals of the form RE2O3 with RE = Lu, Sc or Y are excellent host materials for high power and ultrafast lasers (Krankel, 2015)
For the composition (Er0.07Sc0.50Y0.43)2O3 the melting point is found at temperatures below 2050C
This enabled for the first time, to the best of our knowledge, the growth of a high-quality, large size mixed sesquioxide crystal by the Czochralski method from an iridium crucible
Summary
We re-investigate the binary and ternary phase diagrams of the system Lu2O3–Sc2O3–Y2O3 to identify compositions with reduced melting points suitable for growth by the conventional Czochralski method from standard iridium crucibles. The range of compositions with melting temperatures suitable for the growth from iridium crucibles covers lattice parameters between 10.1 Aand 10.4 A This allows for lattice-matched cubic substrates for epitaxial film growth as well as a wide crystal field tuning of the emission bands of rare-earth-doped sesquioxide laser gain materials. In a proof-of-principle experiment we successfully grow a highquality mixed sesquioxide boule by the Czochralski method for the first time This crystal has an Er-doping concentration of 7 at.% with respect to the cation sites, i.e. a composition of (Er0.07Sc0.50Y0.43)2O3, and exhibits large single crystalline areas. We characterize it with respect to its crystallographic, thermal and spectroscopic properties
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