Impact of Tb doping on luminescence properties of LiCaAlF6 phosphor prepared in argon atmosphere and charge transfer mechanism.

This work focuses on the synthesis and characterization of Tb doped LiCaAlF 6 phosphor for its OSL dosimetry properties. The phosphor has been prepared by melting method. XRD shows the formation of LiCaAlF 6 with enrichment of CaF 2. The excess availability of Ca2+ions are advantageous in incorporation of Tb dopant. The photoluminescence studies show the increase in the luminescence intensity after Tb doping by showing strong emission corresponding to 5D 4 → 7F J (J = 6, 5, 4, 3) transitions with a prominent green emission transition 5D 4 → 7F 5 at 540 nm. Further, Tb ion exist in Tb3+ and Tb4+ state as observed from XPS. The incorporation of Tb4+ ion is difficult to achieve and its presence in the host might also increase the of number of trapping states. The OSL studies of LiCaAlF 6 : Tb show high intensity under blue light stimulation for beta irradiation in the dose range 0.05–10Gy. The OSL sensitivity of LiCaAlF 6 : Tb phosphor is found to be ∼8 times higher to that of commercially available Al 2 O 3 : C. The phosphor has shown dose linearity in the range of 0.05–10Gy and minimum detectable dose (MDD)∼6.95 μGy. The enhanced sensitivity may be attributed to the additional defect centers due to excess CaF 2 with mixed oxidation state of Tb3+ and Tb4+ ions. The enhancement of OSL signal of LiCaAlF 6 : Tb in comparison to Al 2 O 3 :C has been discussed based on charge compensation mechanism. These results indicate that LiCaAlF 6 : Tb phosphor prepared via melting method in Ar gas atmosphere shows good OSL properties and has potential application in radiation dosimetry. • Synthesis of Tb doped LiCaAlF 6 phosphor using melting method in argon atmosphere. • XPS results confirm the co-existence of mixed oxidation state i.e., Tb3+ and Tb4+. • PL spectra confirm the existence of Tb3+ associated defects in LiCaAlF 6 phosphor. • The OSL sensitivity LiCaAlF 6 : Tb phosphor is found to be ∼1.5 times higher than commercially available Al 2 O 3 :C phosphor. • Insight into Tb3+/Tb4+ incorporation in LiCaAlF 6 host and its impact on trapping centers and Tb distribution. [ABSTRACT FROM AUTHOR]