Preparation and Luminescence Spectra of Calcium‐ and Rare‐Earth (R = Eu, Tb, and Pr)‐Codoped α‐SiAlON Ceramics

Abstract

Rare-earth-doped oxynitride or nitride compounds have been reported to be luminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, we report the photoluminescence (PL) spectra of europium-, terbium-, and praseodymium-doped Ca-␣-SiAlON ceramics. The highly dense ceramics were prepared by hot pressing at 1750°C for 1 h under 20 MPa in a nitrogen atmosphere. Europium-doped Ca-␣-SiAlON displayed a single broad emission band peaking at ‫؍‬ 550 -590 nm depending on the europium concentration. The emission bands in the spectra of europium-doped Ca-␣-SiAlONs were assigned to the allowed transition of Eu 2؉ from the lowest crystal field component of 4f 6 5d to 8 S 7/2 (4f 7 ) ground-state level. The emission spectra of terbium-and praseodymium-doped Ca-␣-SiAlON ceramics both consisted of several sharp lines, which were attributed to the 5 D 4 3 7 F j (j ‫؍‬ 3, 4, 5, 6) transitions of Tb 3؉ and 3 P 0 3 3 H j (j ‫؍‬ 3, 4, 5) transitions of Pr 3؉ , respectively. In particular, the terbium-doped ␣-SiAlON ceramics showed a strong green emission among these phosphors.

Photoluminescence properties of β-SiAlON:Yb2+, a novel green-emitting phosphor for white light-emitting diodes

“…Since it is not necessary for β-SiAlON to accommodate the metal ions for charge compensation, rare-earth ions have been confirmed to locate in the continuous channel by electron microscopy [16] or Pr 3+ ), which provide more options for the use in white LEDs [7,11], [17][18][19]. Doping these rare-earth ions into β-SiAlON host lattice also can obtain optimal PL properties.…”

“…Oxynitride or nitride phosphors doped with rare-earth elements often exhibit longer excitation and emission wavelengths than their oxide counterparts, owing to large crystal-field splitting and strong nephelauxetic effect resulting from the coordination of rare-earth ions to nitrogen [1][2][3][4][5][6][7]. Besides, the oxynitride and nitride phosphors are expected to have high thermal and chemical stabilities because their matrices are built on stiff frameworks consisting of Si-N or Al-N tetrahedra [8][9][10].…”

Crystal, electronic and luminescence properties of Eu2+-doped Sr2Al2–xSi1+xO7–xNx

“…a-Sialon is a good example of the first approach, in which Si-N is partially replaced by Al-O in the Si 3 N 4 lattice [13,14]. Eu 2+ -doped Ca-a-sialon shows bright yellow-orange emission upon excitation by blue light [6,7]. In general, starting from a nitride compound is easier than starting from an oxide compound because the nitrogen atom is more flexible in its formation of various chemical bonds with metal and nonmetal atoms (Si, Al, etc.…”

“…With the rapid development of brighter white LEDs for general illumination applications, the use of nitride/ oxynitride phosphors has shown impressive progress in just a few years [4][5][6][7][8][9][10][11][12].…”

Luminescence enhancement of CaMoO4:Eu3+ phosphor by charge compensation using microwave sintering method

“…[4][5][6][7]. However, white LEDs with GaN based blue-emitting chips and yellow-red phosphors have poor color rendering index due to the deficiencies in red emission [8] in current market. In order to solve this problem, two ways are usually recommended for phosphor converted LEDs.…”