Optical spectroscopy of the Sr4Al14O25:Mn4+, Cr3+ phosphor: pressure and temperature dependences. Issue 16 (1st April 2022)

• Record Type: Journal Article
• Authors: Jara, Enrique; Valiente, Rafael; González, Jesus; Espeso, José Ignacio; Khaidukov, Nicholas; Rodríguez, Fernando
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 16(2022)
• Page Start: 6380
• Page End: 6391
• Publication Date: 2022-04-01
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2tc00485b
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : A model to explain the pumping and photoluminescence efficiencies of Mn 4+ -based phosphors is proposed from spectroscopic measurements on Sr4 Al14 O25 :Mn 4+, Cr 3+ . Abstract : We present a spectroscopic study of the doubly Mn 4+ and Cr 3+ -doped Sr4 Al14 O25, synthesised via solid state reaction, as a function of pressure and temperature to check its potential as a red emitting phosphor. The strong crystal field acting on Cr 3+ yields a ruby-like narrow R-line emission that is used as an intrinsic temperature sensor and, in comparison to ruby, provides a fair estimate of the bulk modulus K = 172 GPa for Sr4 Al14 O25 . The photoluminescence (PL) and associated excitation spectra of Sr4 Al14 O25 :Mn 4+, Cr 3+ unravel a strong-field 3d 3 configuration with R 1 and R 2 emission lines largely separated by 10.7 meV, which characterizes the non-centrosymmetric distorted Al4 site in the Sr4 Al14 O25 structure. Eighteen Raman modes have been detected at ambient pressure. They correspond to the stretching modes of the Al–O bonds and show frequency shifts with pressure consistent with Grüneisen parameters ( γ = 0.65), similar to those measured for other aluminates. The variations of PL intensity and lifetime with temperature exhibit a similar concomitant behaviour indicating an efficient pumping to the 4 T 2 level and hence down to the 2 E emitting level in both Mn 4+ and Cr 3+ ions at low and moderate temperatures. Multiphonon non-radiative processes yield a quenching temperature of 400 K for Mn 4+ with an effective activation energy of 0.57 eV. Unexpectedly, this energy decreases with pressure enhancing the non-radiative processes and thus PL intensity reduction. A thoroughly coordinate configurational energy diagram is presented for explaining the main spectroscopic features and excited-state dynamics.