Thermometric and luminescence studies of Eu3+ activated CaSr2(PO4)2 phosphor for non-contact optical thermometry and solid state lighting applications

Abstract

Using a low-cost solution combustion method, CaSr2(PO4)2 orthophosphate phosphors doped with Eu3+ were prepared and examined as non-contact optical thermometers and solid state lighting sources. The synthesized phosphors were characterized via X-ray diffraction (XRD), photoluminescence spectroscopy (PL), Fourier transform infrared spectroscopy (FTIR) and temperature-dependent photoluminescence spectroscopy. The results of XRD and FTIR spectroscopy confirms the creation of a single-phase CaSr2(PO4)2 phosphors with the presence of orthophosphate anion (PO4)3-. Near-ultraviolet stimulation at 395 nm produced intense, orange and red emission bands centered at 592 nm and 615 nm for CaSr2(PO4)2:Eu3+ phosphors, matching the typical 5D0→7F1 and 5D0→7F2 transition states of Eu3+ ions. CIE chromaticity coordinates (0.65, 0.35) in the color gamut confirm the red emission. To accomplish optical thermometry, the fluorescence intensity ratio (FIR) approach was applied, which employed the thermally coupled emission levels 5D1 and 5D0 of Eu3+. With a maximal sensitivity of about 0.0023 K−1 at 323 K, the prepared phosphors are most sensitive at low temperatures. Based on the results obtained, the synthesized phosphor CaSr2(PO4)2:Eu3+ can be exploited in non-contact optical thermometry and solid-state lighting applications.