The luminescence properties of PbWO 4 doped with Gd

3+

have been studied. The PbWO 4:Gd

3+

microcrystal powder was obtained by solid phase reaction method. The microcrystal with strong green emission band was prepared in air with rich oxygen at 875℃ for 10 hours

and the microcrystal with strong blue emission band was prepared in vacuum with active carbon at 800℃ for 8 hours. By measuring the emission of PbWO 4:Gd

3+

for 311nm excited by 274nm

and measuring the excitation spectrum of PbWO 4:Gd

3+

from 200～300nm of 311nm emission

it can be concluded that the luminescence of Gd

3+

in PWO was quenched. So both the excited states 6I 7/2 and 6P 7/2 of Gd

3+

are located in the conduction band of PWO. The luminescence from 4f 4f transition of Gd

3+

is slow

its quenching should not increase the slow components of luminescence of PWO in general

so the luminescence of PWO:Gd is still that of PbWO 4 host dominated by fast components. As a structure sensitive material

PWO is sensitive to oxygen during preparing and annealing. The strong green component of luminescence from PWO:Gd powder compounded in air with rich oxygen is as about 100 times as that of crystal compounded in a atmosphere lack of oxygen

similar to that of crystal sample annealed in air. Its emission and excitation spectra are showed in Fig.1

and the concentration dependence of the peak emission intensity of PWO:Gd is showed in Fig.2. For PWO:Gd prepared in air

the intensity of the green emission of PWO is increased by doping with 50～100ppm Gd. But beyond 100 ppm

Gd doping will quench the luminescence of PWO. For PWO:Gd powder prepared in vacuum with active carbon

its emission is mainly in blue band and the blue emission intensity is increased remarkably as 3～4 times as that from PWO crystal grown by Bridgman method. As shown in Fig.3

the main wide excitation band peaked at 378nm is very different from that prepared and annealed by other method or in other atmosphere. It is a new phenomenon. The new excitation band at 378nm can not excite the green emission. It excites directly the blue centers. The luminescence of PWO doped with low concentration of Gd is stronger than that of pure PWO

and its concentration dependence of the blue band intensity is shown in Fig.4. For PWO:Gd emitting in blue band

prepared in vacuum with active carbon

doping with about 100ppm Gd would improve the luminescence of PWO best

and doping with over 300ppm Gd would make the quenching of PWO luminescence. Low concentration doping of Gd could improve the luminescence intensity of the green and the blue band of PWO. This is not caused by the compensation process of the structural defects of PWO. Because green band and blue band are produced by two different kinds of luminescence centers

these two kinds of luminescence centers could not be compensated by one kind of defects. Mechanism of the Gd

3+

enhancing PWO is probably due to the inverse energy transfer in crystal

Gd

3+

→

PWO host

as the excited states of Gd

3+

are included in the conduction band of PWO host. The PWO doped with Gd is a good scintillating material.