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Understanding the efficiency of Mn4+ phosphors: study of the spinel Mg2Ti1-xMnxO4

Abstract: We present a spectroscopic study of Mn-doped Mg2TiO4 as a function of pressure and temperature to check its viability as a red-emitting phosphor. The synthesis following a solid-state reaction route yields not only the formation of Mn4+ but also small traces of Mn3+. Although we show that Mn4+ photoluminescence is not appreciably affected by the presence of Mn3+, its local structure at the substituted Ti4+ host site causes a reduction of the Mn4+ pumping efficiency yielding a drastic quantum-yield reduction at room temperature. By combining Raman and time-resolved emission and excitation spectroscopies, we propose a model for explaining the puzzling nonradiative and inefficient pumping processes attained in this material. In addition, we unveil a structural phase transition above 14 GPa that worsens their photoluminescence capabilities. The decrease of emission intensity and lifetime with increasing temperature following different thermally activated de-excitation pathways is mostly related to relatively small activation energies and the electric−dipole transition mechanism associated with coupling to odd-parity vibrational modes. A thorough model based on the configurational energy level diagram to the A1g normal mode fairly accounts for the observed excitation and emissionthe quantum yieldof this material.

 Authorship: Jara E., Valiente R., Bettinelli M., Rodríguez F.,

 Fuente: Journal of Physical Chemistry C, 2021, 125(49), 27118-27129

 Publisher: American Chemical Society

 Publication date: 01/12/2021

 No. of pages: 12

 Publication type: Article

 DOI: 10.1021/acs.jpcc.1c08006

 ISSN: 1932-7447,1932-7455

 Spanish project: PGC2018-101464-B-I00

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