Probing into Dopant Concentration Dependent Luminescence Properties of Transition Metal Mn²⁺ Activated Ca- α-SiAlON Orange-Red Phosphors

Volume 2 - Issue 5

Ni J^1,2, Zhou ZZ¹, Xu XK¹, Liu Q^1,2*, Shen FR^3,4, and He LH^3,5,6**

Received: February 29, 2020;   Published: March 11, 2020

DOI: 10.32474/MAMS.2020.02.000146

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Abstract

Transition metal (TM) Mn²⁺activated Ca-α-SiAlON phosphors with compositions of Ca1-_xSi₉Al₃ON₁₅:xMn²⁺(x=0.02~0.16) have been designed and synthesized through a high temperature solid-state reaction. In the polyhedron structure of Ca-α-SiAlON host (P31c), Mn²⁺ions can be accommodated in the lattice without destabalizing the crystal structure, which has been revealed by both XRD and neutron powder diffraction (NPD) characterization. The successful doping of TM Mn²⁺in host was further confirmed by magnetic susceptibility characterization and the occupation of Mn²⁺in lattice was analyzed through Rietveld refinement of crystal structure. The slight left-shift of diffraction peaks in XRD patterns and Gaussian fitting sub-bands of emission spectra all proved that the activators Mn²⁺in Ca-α-SiAlON host not only incorporate into the “separated interstitial sites”, but also modestly substitute for Al³⁺sites. The phosphors mainly deliver orange-red emission centered at ~600nm under UV excitation, which is ascribed to the typical characteristic ⁴T₁(⁴G)→⁶A₁(⁶S) electron transition of divalent Mn^2+.The highest photoluminescence (PL) intensity arrives at x=0.12 of Mn²⁺doping concentration in compositions, then the doping concentration quenching occurs. In addition, through calculating the critical transfer distance, it indicates that the dipole-quadrupole (d-q) interaction is the major mechanism for doping concentration quenching in the phosphors. With the increment of Mn²⁺content up to x=0.12 (quenching concentration), the decay time τ decreases monotonically from 7.5 to 5.5ms, ascribed to the non-radiative energy migration among Mn²⁺ ions in the phosphors.

Keywords: Ca-α-SiAlON: Mn²⁺ phosphor; Magnetic susceptibility; Neutron diffraction; Gaussian fitting; Dipole-quadrupole interaction

Abbreviations: LED: light emitting diodes; CCT: Correlated Color Temperature; TM: transition metal; CRI: Color Rendering Index; NPD :Neutron powder diffraction; TOF: time-of-flight; GPPD: general purpose powder diffractometer; CSNS: China Spallation Neutron Source; GSAS: General Structure Analysis System; MPMS: Magnetic Property Measurement System

Abstract| Introduction| Experimental Work| Characterization and Measurements| Results and Discussion| Conclusion| Acknowledgement| References|