Synthesis of $$\hbox {Tb}³⁺ $$ Tb 3 + ion doped $$\hbox {ZnWO}₄$$ ZnWO 4 phosphors and investigation of their photoluminescence properties: concentration effect

In this paper, the effects of $$\hbox {Tb}³⁺$$ ion concentration on the structural and photoluminescence properties of $$\hbox {ZnWO}₄$$ : $$\hbox {Tb}³⁺$$ have been reported. X-ray diffraction studies indicated that the monoclinic structure of the samples and the crystallinity were found to decrease with the increase of $$\hbox {Tb}³⁺$$ ion concentration due to the distortion in the crystal lattice. The formation of the monoclinic structure was further supported by high resolution transmission electron microscopy and Fourier transform infrared analyses. The transmission electron microscopy image of $$\hbox {ZnWO}₄$$ : $$\hbox {Tb}³⁺$$ (7%) showed a spherical morphology with crystallite sizes in the range of $$\sim $$ 8–12 nm. The excitation spectrum showed a strong broad band originated from the electronic transition within the $$\hbox {WO}₆^6-$$ group. Upon excitation at 270 nm, the prepared $$\hbox {ZnWO}₄$$ : $$\hbox {Tb}³⁺$$ phosphors exhibited sharp and narrow emission peaks, characteristic of the f–f transitions of $$\hbox {Tb}³⁺$$ ions besides a broad band with the maximum at around 460 nm due to the host lattice. The intensity of the broad emission band was found to decrease gradually with the increase of $$\hbox {Tb}³⁺$$ ion concentration and reached minimum at 7 at%. The decay time of the prepared phosphors was investigated in detail and the maximum average lifetime value is found to be 1.187 ms.