掺Gd3+,Y3+对PbWO_4低温热释光的影响

通过热释光方法研究了PbWO₄(PWO),PWO:Y³⁺,PWO:Gd³⁺多晶粉末及PWO,PWO:Y单晶的低温(<300K)热释光现象.多晶粉末中,掺杂Y³⁺或Gd³⁺都会大大降低甚至消除200K附近的热释光峰,同时产生新的热释光峰,分别位于125和150K(掺Y掺Gd).这表明掺三价离子除了起到电荷补偿作用以减少Pb³⁺,O^-浓度外,还可以产生新的陷阱能级.对于PWO:Y单晶,掺杂Y³⁺可以消除253K的热释光峰,即消除较深(～0.89eV)的陷阱,但PWO单晶中较浅的陷阱(～0.42eV)对应130K热释光峰仍然存在,对此进行讨论,它最可能源于氧空位缺陷.根据Pb³⁺,Gd³⁺,Y³⁺的电子库仑势不同,在PWO晶体中替代Pb²⁺后形成的电子陷阱深度有别(E_Pb>E_Gd>E_Y),从而解释了相应的热释光峰值温度的不同 关键词： 4')" href="#">PbWO₄ Y和Gd掺杂 热释光 陷阱

INFLUENCE OF Gd3+ AND Y3+-DOPING ON LOW TEMPERATURE THERMOLUMINESCENCE OF Pb WO_4

The influence of Gd³⁺ and Y³⁺ doping on the low temperature thermoluminescence (TL) of PbWO₄(PWO) is investigated. In the case of polycrystal powder, the TL above 180K is eliminated by doping Y³⁺ or Gd³⁺ ions. Meanwhile, a new TL peak at lower temperature appeare. For the PWO single crystal there are two TL peaks at about 130 and 253K, but only one single peak at about 130K for PWO:Y crystals. The common effect of doping trivalent ions is to decrease or eliminate the TL above 180K and create a new TL peak at lower temperature. It indicates that the traps responsible for TL above 180K are due to the intrinsic defects which probably are Pb³⁺ and O^-. During the preparation of PWO, the evaporation of the PbO component is easier than that of WO₃, which will lead to the deficiency of PbO. The deficiency of O ions can be compensated by annealing in air while the deficiency of Pb is permanent. Therefore in the volume surrounding the Pb vacancy, there is a lack of positive charge. So the charge deficiency in the Pb-sublattic can be most easily balanced by an increase of concentration of Pb³⁺ and O^- Doping Gd³⁺ or Y³⁺ can decrease the concentration of Pb³⁺ and O^-. Gd³⁺ or Y³⁺ can also play a role of electron traps, which create new TL peaks at 150 and 125K, respectively. The trap depth of Gd³⁺ and Y³⁺ are 0.32 and 0.29eV, respectively. The difference between doping Gd³⁺ and Y³⁺ can be explained by the difference between their coulomb potentials.