Spectrally tunable temperature sensitive fluorescence of (Sr _x Ca_(1−x))S:Cu phosphors

Abstract

The present work aims at investigating spectrally tunable temperature sensitive fluorescence of (Sr _x Ca_(1−x))S:Cu; (0 ≤ x ≤ 1) phosphors. Accordingly, these phosphors have been synthesized and their X-ray diffraction (XRD), the excitation and PL emission spectra at room temperature (RT=27°C) and the variation of fluorescence intensity at λ _max, the wavelength of maximum intensity, with temperature have been studied. The XRD measurements confirm the formation of mixed lattice of (Sr _x Ca_(1−x))S. The lattice constant increases linearly with increase in x (within the lattice constants of end members, i.e. CaS and SrS). With appropriate excitation (λ _exc varying from 314 nm to 361 nm) at RT, the peak wavelength (λ _max) of PL emission can be tuned from 428 nm to 523 nm by varying x from 0 to 1. Further the fluorescence intensity at λ _max varies almost linearly with temperature in the range from 40° C to about 140° C. These properties appear to be suitable for thermographic application of these phosphors.