Tm

3+

/Er

3+

/Yb

3+

tri-doped YF

3

powders were synthesized using a facile hydrothermal method. XRD analysis found that the powders were crystallized products.Their sizes and morphologies were characterized by scanning electron micrographs (SEM

Hitachi S-4800)

which indicated that most of the YF

3

powders were in the sizes of hundreds of nanometers.Under 980 nm excitation

we recorded the upconversion spectra at room temperature by Hitachi F-4500.From UV to IR

plenty of upconversion emissions of Tm

3+

and Er

3+

were observed.For Tm

3+

～291 nm emissions come from

1

I

6

→

3

H

6

～347 nm from

1

I

6

→

3

F

4

～362 nm from

1

D

2

→

3

H

6

～452 nm from

1

D

2

→

3

F

4

and～475 nm from

1

G

4

→

3

H

6

can be identified in the upconver-sion spectra.The upconversion emissions from Er

3+

are:～380 nm (

4

G

11/2

→

4

I

15/2

)

～408 nm(

2

H

9/2

→

4

I

15/2

)

～521 nm (

2

H

11/2

→

4

I

15/2

)

～537 nm (

4

S

3/2

→

4

I

15/2

)

～652 nm (

4

F

9/2

→

4

I

15/2

).Therefore

cy-an-white light were observed by naked-eye under 980 nm excitation even for a low excitation power density. With increasing of the excitation power

the emissions firstly become stronger

then weaker

at last nearly dis-appear.There are some discussions on the tempe-rature-dependent upconversion emission spectra

too.Crys-tallization became well after higher temperatures annealing

and all emissions of Tm

3+

and Er

3+

become relatively stronger.Upeonversion spectra depending on Tm

3+

concentration indicate that at relatively low Tm

3+

concentration

Tm

3+

-Er

3+

interaction is dominant

and all Er

3+

emissions become stronger for Tm

3+

transfer energy to Er

3+

.When Tm

3+

concentration reaches about 0.3%

Tm

3+

-Tm

3+

cross relaxation is dominant

and Er

3+

emission relatively become weaker.All Tm

3+

emissions become relatively stronger with Tm

3+

coneentration increasing.From the experimental results

we concluded that the YF

3

powders should be promising materials for up-conversion white light and three-dimensional solid display.