Phosphorus Co-doping Research Articles

Effect of Charge Compensator/Co-dopant Ions on the TL Characteristics of CaSO4:Dy and CaSO4:Tm Phosphors

The effect of charge compensating ions (Na + or P 5+ ) has been studied in CaSO 4 :Dy/Tm phosphors. For CaSO 4 :Dy, Na, the thermoluminescence emission between 380 and 404 K seems to be well correlated with Na co-dopant which increases the formation and stabilisation of the SO 4 - centre. ESR as well as fluorescence measurements also showed an enhanced signal for the SO - 4 radical in CaSO 4 :Dy,Na samples. Co-doping of phosphorus in CaSO 4 :Dy/Tm resulted in increasing the TL sensitivity by about 40% when compared with that in the conventional CaSO 4 :Dy/Tm TL phosphors. In CaSO 4 :Dy,P and CaSO 4 :Dy, while ESR measurements showed no change in ESR signal intensity, TL measurements showed higher intensity for CaSO 4 :Dy,P samples. On the other hand, addition of Zr 4+ to CaSO 4 :Dy did not result in any enhancement in TL intensity of the dosimetric peak; however, ESR measurements showed enhanced intensity for the SO 3 - radical (stable up to 300°C) in CaSO 4 :Dy,Zr. These results tend to show that charge compensator ions such as Na + and P 5+ when present in CaSO 4 :Dy/Tm, result in higher luminescence efficiency either due to better incorporation of activator ions or due to improvement in energy transfer processes. On the other hand incorporation of co-dopant ions with higher effective charge such as Zr 4+ would increase the concentration of cation vacancies but did not result in an increase in the luminescence efficiency.

Degradation induced by the Sr 2+ vacancies in SrS:Ce electroluminescent devices

The degradation mechanism of SrS:Ce electroluminescent (EL) devices is proposed. Degradation is induced by the Sr 2+ vacancies in a SrS phosphor film. The Sr 2+ vacancies are formed by Ce doping and S excess deposition condition. Ce has a special influence on Sr 2+ vacancy formation in comparison with other trivalent rare-earth ions because of the partial existence of Ce 4+. We have found that phosphorus codoping, which quenches the Sr 2+ vacancies, drastically improves the stability of SrS:Ce EL devices.

ChemInform Abstract: Preparation of Cerium‐Activated Silica Glasses: Phosphorus and Aluminum Codoping Effects on Absorption and Fluorescence Properties.

AbstractCe‐doped SiO2 glasses have been prepared by plasma torch chemical vapor deposition and their optical properties are compared to those of Ce‐P‐ and Ce‐Al‐codoped silica glasses (codoping by plasma torch soot remelting).

Preparation of Cerium‐Activated Silica Glasses: Phosphorus and Aluminum Codoping Effects on Absorption and Fluorescence Properties

Cerium‐activated silica (SiO2) glasses were prepared by plasma torch chemical vapor deposition (CVD). In Ce‐doped SiO2 glasses, most Ce exists as Ce4+ ions; the remaining small amount of Ce3+ ions exhibits a broad fluorescence spectrum with a large Stokes shift, ∼9600 cm‐1, from the excitation spectrum peak of 324 nm. Aluminum and phosphorus codoping considerably increases the Ce3+ ratio and shifts the peaks of both spectra to shorter wavelengths. P codoping is the more effective way to achieve this result and in some cases produces an absorption spectrum similar to that of a Ce‐doped phosphate glass. These findings are consistent with the solvatiorn shell model for codoping, as previously proposed. To codope P, a soot remelting method was devised to deal with the highly volatile P2O5.