Appl Phys A (2009) 94: 607–612
DOI 10.1007/s00339-008-4861-z
UV excitable Y
2−x−y
Gd
y
SiO
5
:Ce
x
phosphors for cool white light
emission
P. Thiyagarajan · Brajesh Tiwari · M. Kottaisamy ·
N. Rama · M.S. Ramachandra Rao
Received: 15 August 2007 / Accepted: 7 August 2008 / Published online: 10 September 2008
© Springer-Verlag 2008
Abstract Cool white light was realized in Y
2−x−y
Gd
x
SiO
5
:
Ce
y
phosphor under near UV excitation, due to the occupa-
tion Ce
3+
in Y
3+
1st and 2nd site, synthesized using solid
state carbothermal reduction route. SEM with elemental
analysis show the existence of Gd in Y
2
SiO
5
:Ce enhances
the particles size in comparison to Y
2
SiO
5
:Ce phosphors
alone. Gd
3+
(0.00 ≤ x ≤ 0.75) and Ce
3+
(0.02 ≤ y ≤ 0.10)
concentration was optimized to 0.50 and 0.08 in Y
2
SiO
5
,
respectively. The CIE chromaticity color coordinates (0.24,
0.20) are close to cool white light value which could be use-
ful for the fabrication of cool white LED.
PACS 78.55.-m · 71.35Cc · 71.70Ej
P. Thiyagarajan (
) · B. Tiwari · N. Rama ·
M.S. Ramachandra Rao
Materials Science Research Centre, Indian Institute
of Technology Madras, Chennai 600 036, India
e-mail: thiyagu@physics.iitm.ac.in
Fax: +91-44-22575909
P. Thiyagarajan · B. Tiwari · N. Rama ·
M.S. Ramachandra Rao (
)
Department of Physics, Indian Institute of Technology Madras,
Chennai 600 036, India
e-mail: msrrao@iitm.ac.in
Present address:
P. Thiyagarajan
Laboratory for Advanced Molecular Processing, Department
of Chemical Engineering, Pohang University of Science
and Technology, Pohang 790 784, South Korea
M. Kottaisamy
Materials Research Laboratory, Kalasalingam University,
Krishnan Kovil, TN, India
1 Introduction
Utilization of phosphor in industry has resulted in its
tremendous growth. These find enormous applications as
light emitting diodes (LEDs), field emission displays
(FEDs), cathode ray tubes (CRT) vacuum fluorescent dis-
plays (VFDs), plasma display panels (PDPs), and X-ray
imaging scintillators. Most of the phosphors used today are
either oxide or sulfide based phosphors. Oxide phosphors
are more stable and inert against the degradation in chemi-
cal and thermal properties compared to sulfide based ones,
and are used in the screen of PDPs [1, 2].
Rare earth elements doped oxide phosphors have su-
perior emission properties compared to phosphors doped
with transition metal ions, which has attracted the atten-
tion of researchers and industrialists. Rare earth activated
Y
2
SiO
5
phosphors synthesized via various routes such as
flame spray pyrolysis [3, 4], PLD [5–7], co-precipitation
process [8], solid state reaction [9], hydrothermal method
[10], sol–gel method [11–14], melting salt assisted sol–gel
method [15] have been used to study the physical, chem-
ical and luminescent properties. Ce
3+
activated Y
2
SiO
5
is
an efficient blue phosphor under the excitation of near UV
light (365 nm). The luminescent property of this phosphor
has been studied for several decades. Y
2
SiO
5
exists in two
phases, namely X
1
and X
2
in which X
1
phase forms be-
low 1190°C, whereas X
2
phase forms above this tempera-
ture with space groups P2
1
/c and B2/c, respectively [16].
Both polymorphs crystallize in monoclinic structure with
two Y
3+
sites having the coordination numbers 9(A
1
) and
7(A
2
) for X
1
and 7(B
1
) and 6(B
2
) for X
2
phase [16, 17],
where A
1
,A
2
,B
1
, and B
2
are two Y
3+
sites in X
1
and
X
2
phase, respectively. The number of Si bonded oxygens
is 8 and 4 for A
1
and A
2
in X
1
phase, while the number
of free oxygens is 1 and 3 for A
1
and A
2
, respectively, in