Y

2

O

3

has highly chemical durability

thermal stability and a relatively low phonon energy(430~550 cm

-1

).These aspects make Y

2

O

3

a promising host for upconversion applications.Y

1.98

Yb

0.01

Er

0.01

O

3

nanocrystalline powders were prepared via a co-precipitation method using nitrates

ammonia and ammonium hydrogen carbonate as raw materials.The X-ray diffraction results showed that the as-prepared powders were cubic phase of Y

2

O

3

after fired at 700℃ for 2 h.Field emission scanning electronic microscopy revealed that most of the particles were nearly spherical and the average diameter of the particles was in the range of 60~80 nm.The upconversion spectroscopic properties of the powders were investigated under the excitation of a 980 nm continuous wave diode laser.Strong red and green upconversion emissions which centered at 660 nm and 562 nm respectively were observed.The red emission was assigned to the transitions of

4

F

9/2

→

4

I

15/2

energy levels of Er

3+

ions

while the green emission was attributed to the transitions of

2

H

11/2

/

4

S

3/2

→

4

I

15/2

energy levels of Er

3+

ions.The dependence of the intensity of upconversion emissions upon the excitation power of the diode laser suggested that two-photon absorption processes are involved in the green and red upconversion luminescence.The excited state absorption of Er

3+

ions and the energy transfer from Yb

3+

to Er

3+

ions are main upconversion mechanisms.Due to its highly efficient upcovnersion luminescence

this material could find applications in the fields of fluorescent labels and infrared detection.