Photoluminescence behavior of Eu3+ ion doped into γ- and α-alumina systems prepared by combustion, ceramic and Pechini methods

✍ Scribed by M.A.F. Monteiro; H.F. Brito; M.C.F.C.M. Felinto; G.E.S. Brito; E.E.S. Teotonio; F.M. Vichi; R. Stefani

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 554 KB
• Volume: 108
• Category: Article
• ISSN: 1387-1811
• DOI: 10.1016/j.micromeso.2007.03.045

✦ Synopsis

Al 2 O 3 :Eu 3+ (1%) samples were prepared by combustion, ceramic, and Pechini methods annealed from 400 to 1400 °C. XRD patterns indicate that samples heated up to 1000 °C present disordered character of activated alumina (c-Al 2 O 3 ). However, a-Al 2 O 3 phase showed high crystallinity and thermostability at 1200-1400 °C. The sample characterizations were also carried out by means of infrared spectroscopy (IR), scanning electron microscopy (SEM) and specific surface areas analysis (BET method). Excitation spectra of Al 2 O 3 :Eu 3+ samples present broaden bands attributed to defects of Al 2 O 3 matrices and to LMCT state of O ! Eu 3+ , however, the narrow bands are assigned to 7 F 0 ! 5 D J , 5 H J and 5 L J transitions of Eu 3+ ion. Emission spectra of samples calcined up to 1000 °C show broaden bands for 5 D 0 ! 7 F J transitions of Eu 3+ ion suggesting that the rare earth ion is in different symmetry sites showed by inhomogeneous line broadening of bands, confirming the predominance of the c-alumina phase. For all samples heated from 1200 to 1400 °C the spectra exhibit narrow 5 D 0 ! 7 F J transitions of Eu 3+ ion indicating the conversion of c to a-Al 2 O 3 phases, a high intensity narrow peak around 695 nm assigned to R lines of Cr 3+ ion is shown. Al 2 O 3 :Eu 3+ heated up to 1100 °C presents an increase in the X 2 intensity parameter with the increase of temperatures enhancing the covalent character of metal-donor interaction. The disordered structural systems present the highest values of emission quantum efficiencies (g). CIE coordinates of Al 2 O 3 :Eu 3+ are also discussed.