Various Al2O3 polymorphs, such as α, β, and γ phases, have been synthesized and extensively studied [1]. Among them, α-phase Al2O3 has received much attention because of its high thermal stability and good luminescence properties. The crystal structure of α phase is of the “corundum” or “sapphire” type. To the best of our knowledge, no data is available on the solubility limit of Eu3+ ions in Al2O3. There has also been no any data on the temperature dependence of the luminescence properties of Eu3+ in Al2O3 from cryogenic to higher temperatures than 300 K.