Dysprosium-activated scheelite-type oxides as thermosensitive phosphors

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 7; no. 25; pp. 761 - 768
• Main Authors: Perera, S. Sameera, Rabuffetti, Federico A
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2019
• Subjects: Charge transfer; Dysprosium; Optical measuring instruments; Oxides; Parameter sensitivity; Phosphors; Scheelite; Temperature; Temperature dependence
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c9tc00795d

Scheelite-type oxides of formulas NaLa 1− x Dy x (MO 4 ) 2 and Na 5 La 1− x Dy x (MO 4 ) 4 (M = Mo, W) were investigated as thermosensitive phosphors in the 300-700 K temperature range. Phosphors were synthesized in the solid state and their thermometric responses were quantitatively interrogated using the luminescence intensity ratio approach. Temperature-dependent blue emissions from the thermally coupled levels 4 I 15/2 (454 nm) and 4 F 9/2 (484 nm) of Dy 3+ were observed under steady-state ultraviolet excitation of the oxygen-to-metal charge-transfer state. The ratio between the integrated intensities of these emission bands was used as the thermometric parameter. Relative thermometric sensitivities were systematically mapped as a function of host composition and activator concentration. At 350 K, the highest relative sensitivity was observed for Na 5 La 0.5 Dy 0.5 (WO 4 ) 4 (1.8 × 10 −2 K −1 ), while at 700 K the sensitivity was maximum for NaDy(MoO 4 ) 2 (3.8 × 10 −3 K −1 ). Comparison of these values with those reported for other dysprosium-activated phosphors revealed the potential of scheelite-type oxides as optical sensors for intermediate temperatures (<1000 K). A systematic investigation of the thermometric response of dysprosium-activated scheelite-type oxides demonstrates their potential as optical sensors for intermediate temperatures.