Amorphous Si₃B₃N₇ Ceramic as a Versatile Host for Inorganic Phosphor Activators

Abstract

460www.MaterialsViews.com wileyonlinelibrary.com . IntroductionIn comparison with the conventional lighting technologies, e.g. incandescent and fl uorescent lamps, LED-based solid state lighting devices provide remarkable improvements in terms of durability, compactness, designability, environmental friendliness and, most importantly, energy effi ciency. [1][2][3][4][5][6] In this recent lighting technology, wavelength conversion phosphors play a crucial role, and great efforts have been made to explore new phosphors with improved overall performance. Luminescent materials described up to now are mainly based on crystalline matrices, where photoluminescence is achieved by replacing suitable ions of the crystalline host with luminescent ones, commonly Eu 2+ , Ce 3+ or Tb 3+ , which are called activators. The chemical and crystal chemical properties of the activator ions, in particular size and charge, must correspond to those of the cations to be substituted in the host lattice. Obviously, these requirements impose limitations in identifying suitable combinations of crystalline hosts and activator ions. As another disadvantage, previously described luminescent materials are commonly produced via solid state reactions at high temperatures requiring long reaction times, including repeated grinding and heating cycles. [ 3,7 ] Among those phosphors considered for applications are rare-earth doped nitridosilicate based materials, which exhibit superior chemical, thermal, and radiation stability compared to oxide, sulphide and halide based phosphors or combinations thereof. [8][9][10][11][12][13][14][15] In particular, the luminescent properties of rare earth ions, which emit radiation via 5d → 4f transitions, such as Eu 2+ and Ce 3+ , are dramatically affected by the large covalency of N 3− ions. As a result, the centres of gravity of the 5d levels are shifted to positions lower in energy (nephelauxetic effect), [ 16 ] leading to longer wavelength emission bands, providing a red component needed for the fabrication of white-LEDs.With the aim of circumventing the drawbacks mentioned inherent to doped crystalline luminescent materials, and at the same time keeping the advantages of high thermal and radiation stability of nitridosilicates, and also of nitrogen ions as coordinating ligands, we have developed the novel approach of using nitride based inorganic random networks as hosts, for which the cationic network sites are not accessible to the rare earth activator elements because of incompatible size and bonding properties. Instead, the activator elements act as network modifi ers, with the far reaching consequence that activators of any size and charge can be easily incorporated in quite variable concentrations. We regard the further options of co-doping two or more activators and sensitizers into the same matrix as a substantial advantage over the conventional approaches based on crystalline materials. Here, we report on the realization of such an innovative concept, and present a novel family of phosphors based on a...

Synthesis and processing of silicon nitride and related materials using preceramic polymer and non-oxide sol-gel approaches

“…The photoluminescence spectrum of Si3B3N7 shows three distinct emissions corresponding to the nanoscale Si-rich, B-rich and intermediate domains [251]. Addition of the hexamethyldisilazides of Eu, Ce or Tb resulted in bright phosphors in which the lanthanide ions were dispersed through an amorphous matrix [252]. Interestingly some of these phosphors showed different emission colours at different excitation wavelengths (Fig.…”

“…Photoluminescence spectra of Tb 3+ -doped amorphous Si3B3N7 ceramic showing the change in the spectrum with excitation wavelength and (inset) photographs showing the emission colour at various excitation wavelengths. Reproduced with kind permission from[252].…”

Synthesis and processing of silicon nitride and related materials using preceramic polymer and non-oxide sol-gel approaches

“…The photoluminescence spectrum of Si3B3N7 shows three distinct emissions corresponding to the nanoscale Si-rich, B-rich and intermediate domains [251]. Addition of the hexamethyldisilazides of Eu, Ce or Tb resulted in bright phosphors in which the lanthanide ions were dispersed through an amorphous matrix [252]. Interestingly some of these phosphors showed different emission colours at different excitation wavelengths (Fig.…”

“…Photoluminescence spectra of Tb 3+ -doped amorphous Si3B3N7 ceramic showing the change in the spectrum with excitation wavelength and (inset) photographs showing the emission colour at various excitation wavelengths. Reproduced with kind permission from[252].…”

Computational study of impact of composition, density, and temperature on thermal conductivity of amorphous silicon boron nitride

“…Potential applications of a‐SiBN include ceramic parts and fibers as well as protective coatings . Recently, Eu 2+ and Ce 3+ doped amorphous Si 3 B 3 N 7 ceramics have been proposed as luminescent materials in white LEDs . Synthesis of SiBN ceramic fibers follow the polymer‐to‐ceramic route .…”

Enhancement of encaged electron concentration by Sr 2+ doping and improvement of Gd 3+ emission through controlling encaged anions in conductive C12A7 phosphors

“…Usually, for oxide based materials, the doping strategy can modify their crystal structures and affect their physical and chemical properties. [11][12][13] For example, Chavhan et al reported the structural and optical properties of 6CaOÁ6SrOÁ7Al 2 O 3 thin films and found that the transparency decreased with increasing Sr 2+ doping concentration. 14 In addition, the reported studies show that 12SrOÁ7Al 2 O 3 (S12A7) possesses a similar cage structure to C12A7 and a larger lattice constant (a = 1.233 nm) than C12A7 (a = 1.199 nm).…”

Synthesis and processing of silicon nitride and related materials using preceramic polymer and non-oxide sol-gel approaches

“…The photoluminescence spectrum of Si3B3N7 shows three distinct emissions corresponding to the nanoscale Si-rich, B-rich and intermediate domains [251]. Addition of the hexamethyldisilazides of Eu, Ce or Tb resulted in bright phosphors in which the lanthanide ions were dispersed through an amorphous matrix [252]. Interestingly some of these phosphors showed different emission colours at different excitation wavelengths (Fig.…”

“…Photoluminescence spectra of Tb 3+ -doped amorphous Si3B3N7 ceramic showing the change in the spectrum with excitation wavelength and (inset) photographs showing the emission colour at various excitation wavelengths. Reproduced with kind permission from[252].…”

Computational study of impact of composition, density, and temperature on thermal conductivity of amorphous silicon boron nitride

“…Potential applications of a‐SiBN include ceramic parts and fibers as well as protective coatings . Recently, Eu 2+ and Ce 3+ doped amorphous Si 3 B 3 N 7 ceramics have been proposed as luminescent materials in white LEDs . Synthesis of SiBN ceramic fibers follow the polymer‐to‐ceramic route .…”

Enhancement of encaged electron concentration by Sr 2+ doping and improvement of Gd 3+ emission through controlling encaged anions in conductive C12A7 phosphors

“…Usually, for oxide based materials, the doping strategy can modify their crystal structures and affect their physical and chemical properties. [11][12][13] For example, Chavhan et al reported the structural and optical properties of 6CaOÁ6SrOÁ7Al 2 O 3 thin films and found that the transparency decreased with increasing Sr 2+ doping concentration. 14 In addition, the reported studies show that 12SrOÁ7Al 2 O 3 (S12A7) possesses a similar cage structure to C12A7 and a larger lattice constant (a = 1.233 nm) than C12A7 (a = 1.199 nm).…”

Synthesis and processing of silicon nitride and related materials using preceramic polymer and non-oxide sol-gel approaches

“…The photoluminescence spectrum of Si3B3N7 shows three distinct emissions corresponding to the nanoscale Si-rich, B-rich and intermediate domains [251]. Addition of the hexamethyldisilazides of Eu, Ce or Tb resulted in bright phosphors in which the lanthanide ions were dispersed through an amorphous matrix [252]. Interestingly some of these phosphors showed different emission colours at different excitation wavelengths (Fig.…”

“…Photoluminescence spectra of Tb 3+ -doped amorphous Si3B3N7 ceramic showing the change in the spectrum with excitation wavelength and (inset) photographs showing the emission colour at various excitation wavelengths. Reproduced with kind permission from[252].…”

Computational study of impact of composition, density, and temperature on thermal conductivity of amorphous silicon boron nitride

“…Potential applications of a‐SiBN include ceramic parts and fibers as well as protective coatings . Recently, Eu 2+ and Ce 3+ doped amorphous Si 3 B 3 N 7 ceramics have been proposed as luminescent materials in white LEDs . Synthesis of SiBN ceramic fibers follow the polymer‐to‐ceramic route .…”

Enhancement of encaged electron concentration by Sr 2+ doping and improvement of Gd 3+ emission through controlling encaged anions in conductive C12A7 phosphors

“…Usually, for oxide based materials, the doping strategy can modify their crystal structures and affect their physical and chemical properties. [11][12][13] For example, Chavhan et al reported the structural and optical properties of 6CaOÁ6SrOÁ7Al 2 O 3 thin films and found that the transparency decreased with increasing Sr 2+ doping concentration. 14 In addition, the reported studies show that 12SrOÁ7Al 2 O 3 (S12A7) possesses a similar cage structure to C12A7 and a larger lattice constant (a = 1.233 nm) than C12A7 (a = 1.199 nm).…”