Optical Properties of CaS and CaS:Eu 2+ Crystals
Tae-Hwan Bang · Sung-Hyu Choe ∗
Department of Physics, Chosun University, Gwangju 501-759, Korea (Received 16 July 2014 : revised 22 July 2014 : accepted 22 July 2014)
An X-ray diffraction (XRD) analysis revealed that CaS and CaS:Eu
2+crystals had a cubic struc- ture. The lattice constants of these samples were a = 5.6961 ˚ A for the CaS crystals, and a = 5.6944
˚ A for the CaS:Eu
2+crystals. The direct and the indirect energy gaps were 5.510 and 5.501 eV for the CaS crystal and 3.401 and 3.041 eV for the CaS:Eu
2+crystal, respectively, at 293 K. The photoluminescence spectra were measured in the wavelength range of 250 nm ∼ 950 nm at 293 K.
A broad emission peak was observed near 508.2 nm for CaS. A high-intensity emission peak due to the Eu
2+ion was observed near 648.1 nm for CaS:Eu
2+. This PL peak was attributed to radiative transitions between the split electron energy levels of the Eu
2+ions which occupy the O
hsymmetry sites of the CaS:Eu
2+crystal’s host lattice.
PACS numbers: 78.20.-e
Keywords: CaS and CaS:Eu
2+, Optical absorption, Energy gaps, Photoluminescence, Eu
2+ion
CaS õ m Í CaS:Eu 2+ + s ÇX N Ë8 ý ° Ë Ñ] K ¡X ì Ä ¤V R Ë
ç
¡? Z 9 · L |) ç ³ × ∗
¸ @ / < Æ § Ó ü t o < Æõ , F g Å Ò 501-759
(2014¸ 7 Z 4 16{ 9 ~ Ã Î6 £ §, 2014¸ 7 Z 4 22{ 9 Ã º& ñ : r ~ Ã Î6 £ §, 2014¸ 7 Z 4 22{ 9 > F S X & ñ )
CaS x 9 CaS:Eu (0.1 mol%) & ñ ` ¦ $ í © # $ í © ) a & ñ _ ½ ¨ ¸ü < © à º\ ¦ ½ ¨ % i . $ í © ) a CaS x 9 CaS:Eu & ñ _ & ñ ½ ¨ ¸ H { 9 ~ ½ Ó^ ½ ¨ ¸s ¦ © à º H a
0= 5.6961 ˚ A, a
0= 5.6944 ˚ A s % 3
. s [ þ t & ñ _ F gf ¨ Ã º Û ¼& 7 à Ô! 3 É r 8 £ ¤& ñ r « Ñ_ : r ¸\ ¦ 293 K Ð Ä »t ¦, 200 ∼ 850 nm © % ò % i
\
" f 8 £ ¤& ñ % i Ü ¼ 9 l í f ¨ à ºé ß % ò % i \ " f 8 £ ¤& ñ ) a F gf ¨ à º Û ¼& 7 à Ô! 3 Ü ¼ РÒ' F g < Æ& h \ -t ç ß ` ¦ > í
ß % i . CaS x 9 CaS:Eu & ñ _ F g µ 1 Ï F g : £ ¤$ í É r 293 K \ " f 250 nm ∼ 950 nm # 3 0 A_ F g µ 1 Ï F g Û ¼& 7 à
Ô! 3 ` ¦ 8 £ ¤& ñ # ½ ¨ % i . F g µ 1 Ï F g Û ¼& 7 à Ô! 3 Ü ¼ ÐÂ Ò' CaS & ñ É r 508.2 nm % ò % i \ " f ; ¤ s V , ¦ \ V o
t · ú § É r F g µ 1 Ï F g x ß ¼ ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, CaS:Eu & ñ \ " f H 495.2 nm ü < 648.1 nm % ò % i \ " f F g µ 1 Ï F
g x ß ¼ ' a8 £ ¤ ÷ &% 3 . 648.1 nm % ò % i \ " f ' a8 £ ¤ ) a F g µ 1 Ï F g x ß ¼ H ' ô Ç Eu Ô ¦í HÓ ü t \ l ô Ç F g µ 1 Ï F
g x ß ¼ Ð" f & ñ © s : r \ _ , CaS ¸^ & ñ _ Ca\ @ /u # [ þ t # Qç ß europium Ô ¦í HÓ ü t s ¸
^
_ O
h@ /g A& h \ Eu
2+s : r Ü ¼ Ð 0 Au ¦ Eu
2+s : r _ ì r o ) a \ -t ï r 0 Aç ß _ 4 ¤ s \ _
ô Ç x ß ¼ Ð K $ 3 ) a .
PACS numbers: 78.20.-e
Keywords: CaS x 9 CaS:Eu
2+, F gf ¨ Ã º, F g < Æ& h \ -t ç ß , F g µ 1 Ï F g : £ ¤$ í , Eu
2+s : r
∗
