Structural, mechanical, electrical and optical properties of NaxK1-xCl:Ce3+ crystals grown in large size by the Czochralski method

Abstract

Large-sized single crystals of NaxK1-xCl:0.01Ce3+ (with x = 0.2, 0.4, 0.5, 0.6 and 0.8) have been grown by the Czochralski method. The structural, mechanical, electrical and optical properties were characterized by carrying out X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), micro-hardness, DC/AC electrical, optical absorption and luminescence measurements. XRD analysis indicates the two-phased (with two f.c.c. lattices) nature of the mixed crystals and the incorporation of Ce3+ ions into the NaxK1-xCl crystal matrix. XPS analysis has verified the dominant presence of Ce3+ (over Ce4+) ion in the NaxK1-xCl crystal matrix. Hardness measurement has shown an increase of crystal hardness with Ce3+ doping and maximum hardness for the Na0.5K0.5Cl:0.01Ce3+ crystal. Electrical measurements indicate that the DC/AC electrical conductivity, dielectric loss factor and dielectric constant of Ce3+ doped crystals increase with the increase in temperature and are larger than that for the un-doped Na0.5K0.5Cl crystal. Four peaks at 203, 215, 290 and 344 nm are shown by the optical absorption spectra. Photoluminescence excitation and emission peaks due to Ce3+ (4f↔5d) transitions have got influenced by the Ce3+ doping. The TL glow curves of NaxK1-xCl:0.01Ce3+ crystals obtained show two peaks at about 72 and 174 °C, Ce3+ ions produce suitable trap depth and result in the characteristic emission. The Na0.5K0.5Cl:Ce3+ crystal is found to exhibit maximum PL and TL performances. Results obtained indicate that the NaxK1-xCl:Ce3+ crystals grown can find their use in luminescence, capacitor and thermoluminescence dosimeter applications.