Photoluminescence and optical properties of Eu3+/Eu2+-doped transparent Al2O3 ceramics

Abstract Transparent Eu3+-doped (0.05 -0.15 at. %) alumina ceramics with fine-grained microstructure were prepared and studied in terms of optical properties and photoluminescence (PL). The light transmission through ceramics up to dopant concentrations 0.125 at. % is dominated by birefringence scattering at grain boundaries. As confirmed by HRTEM/EDS element mapping, high photoluminescence intensity was achieved as the result of the dopant segregation at grain boundaries. The PL emission spectra of Al2O3:Eu3+ ceramics exhibited red light emissions with the highest intensity (394 nm excitation) for material containing 0.125 at. % of Eu3+. The luminescence decay was single-exponential with a lifetime ∼1.5 ms. The post-sintering reduction of Eu3+→Eu2+ under an H2 atmosphere (at 1300 °C) was difficult. Two simultaneously coexisting Eu2+ emitting PL centers were identified, one emitting blue light with average decay constant of 150 ns, and the other green light (more intense) with average decay constant of 1.3 μs.