Rare earth doped nanocrystalline ZrO

2

have attracted great interest. For zirconium oxide has a low phonon energy of about 470 cm

-1

and a high refractive index of about 2.1 and is chemically and thermally stable. And rare earth ions

especially erbium

have played an important role in the development of optical communication technology during the past few decades. Recently

erbium doped luminescent materials have received considerable attention for its luminescence and frequency upconversion of infrared radiation into the visible region. The nanocrystalline ZrO

2

:Er

3+

powders with room temperature sharp characteristic emissions were prepared by co-precipitation method. The main work concerns the structures

the luminescence emissions and upconversion emissions change of nanoparticles with the sintering temperature. For ZrO

2

sintered at 600℃ the spectra is dominated by the peaks centered at 30.28 (101)t characteristic of the tetragonal structure. For ZrO

2

sintered at 800℃ the spectra is dominated by the peaks centered at 28.35(-1

1

1)m and 31.65(1

1

1)m characteristic of the monoclinic structure

but there also exist the tetragonal structure. The tetragonal structure almost totally converts to the monoclinic structure for ZrO

2

sintered at 950℃. The luminescence emissions contain the blue emission and the green emission. The intensity of the blue emission is greater than that of the green emission. There exist two emission centers of Er

3+

in different crystalline phases. One is monoclinic phase

and the other is tetragonal phase. We also find that the emission intensity reaches the maximum value when the ratio of the tetragonal phase to the monoclinic phase comes to a certain value. The room temperature upconversion emission of these samples is also observed and the upconversion emission mechanism is given. We find that the quadratic dependence of the green emissions on excitation power indicates that a two-photon absorption process occurs under 976nm excitation. The effect of the doped concentration of Er

3+

on the fluorescence emission intensity has been discussed

and the concentration quenching will occur when the concentration of Er

3+

is more than 0.9% (atomic fraction) Er

3+

.