Tunable Luminescence of CeAl₁₁O₁₈Based Phosphors by Replacement of (AlO)⁺by (SiN)⁺and Co-Doping with Eu

Abstract

A series of Si-N or Eu-Li doped CeAl 11 O 18 and CeAl 12 O 18 N phosphors are prepared by solid-state reaction. Their structure and luminescence are researched carefully. Si-N doping with the concentration less than 8% can be successfully dissolved into CeAl 11 O 18 crystal lattice and doesn't change the matrix structure, only resulting in crystal lattice shrinkage due to the shorter bond length for Si-N bond versus Al-O bond. It is observed that blue emission gradually decreases and UV emission becomes stronger due to the gradual disappearance of O Me ions with the increase of Si-N doping. 1-7 These phosphors show some features of high quantum yield, chemical and radiation stability, which make them still under research in many areas now. It is demonstrated here that some aluminates will show very interesting results by tuning the crystal structure slightly, despite (oxy)nitride based phosphors are researched widely and greatly developed recently due to their high quantum efficiency, excellent thermal, physical and chemical stabilities, and therefore show large potential to be implemented in highly efficient and reliable white LEDs. [8][9][10] Generally, the hexagonal aluminates are divided into three different groups:11-13 1. compounds MeAl 12 O 19 (Me = Ca, Sr, Eu) with magnetoplumbite-type structure; 2. compounds MeMgAl 10 O 17 (Me = Ba, Sr, Eu) with β-alumina structure; 3. distorted magnetoplumbitetype structure such as CeAl 11 O 18 . The β-alumina structures and magnetoplumbite are both composed of spinel blocks formed by the close packing of Al and O atoms. There is the merely significant difference in the two mirror planes (z = 0.25 and 0.75) between these two structures. In the β-alumina structure, each mirror plane contains one large cation and one oxygen. The non-close-packed mirror plane is connected with the stable spinel blocks closely. In the magnetoplumbite structure, the mirror planes contain one large cation and more oxygens 1. Generally, CeAl 11 O 18 is considered to have distorted magnetoplumbite structure. The difference from the normal magnetoplumbite-type structure is that La (Ce) large ions are considered to be partially replaced by O ions, O Me as an abbreviation.11 O Me is present because of non-ideal stoichiometry of CeAl 11 O 18 with respect to the ideal MeAl 12 O 19 composition for magnetoplumbite structure (large-cation/small-cation/anion = 1/12/19). Just due to this disorder, CeAl 11 O 18 exhibits special luminescence properties, which will be discussed later.Within those hexagonal aluminates, as a kind of self-activated phosphor, CeAl 11 O 18 shows very interesting characteristics, i.e. two emission peaks one UV band at ∼350 nm and one main blue band at ∼460 nm respectively. As we know, UV light can kill bacteria effectively and blue light is essential in photosynthesis for green plant. Due to its special luminescence properties, CeAl 11 O 18 based phosphors have been applied in sterilization, therapeutic, cosmetic skin treatment and promoting plant growth in greenhouse.14 To meet...

Growth and characterization of large CeAlO3 perovskite crystals

“…Namely, under 266 nm excitation these crystals show an intense complex luminescence band in the blue-yellow spectral range peaked at 476 nm (Fig.8b). Previously such luminescence under photoexcitation was also reported in СеAlO3 crystals [19]. It was suggested that not the host, but the admixture CeAl11O18 phase is responsible for this emission.…”

Functionally Graded Al2O3–CTZ Ceramics Fabricated by Spark Plasma Sintering

“…In sample STD1200, neither a CeAlO 3 nor a CeAl 11 O 18 phase was detected, but with increasing temperature, CeAlO 3 was identified in small amounts at 1250 °C. The CeAl 11 O 18 phase only appeared in the composition at high sintering temperatures (1300 °C), proving that it forms at high temperatures [ 52 ]. For the asymmetric graphite configuration, the CeAl 11 O 18 phase appeared in all the samples, and its amount increased with sintering temperature shown by the increasing intensity of its diffraction peaks.…”

Luminescent properties of a novel Al10O3N8:Eu2+ phosphor by a mechanochemical activation route

“…However, the luminescence intensity of Al 10 O 3 N 8 :Eu 2+ phosphor still cannot be comparable with commercial BAM:Eu 2+ phosphor. Inspired by the doping favoring improved luminescence [28,29], the effect of Si-N substitution for Al-O bond on the luminescence is investigated preliminarily. Amazingly, the luminescence intensity is notably increased after Si-N doping.…”