Versatile Ca2LnSbO6:Eu3+/Mn4+ (Ln = La,Y, Gd,and Lu) phosphors for temperature sensing and plant growth LED

A multifunctional double-perovskite-type Ca₂LnSbO₆ (Ln = La, Y, Gd, and Lu) phosphors with Eu³⁺ and Mn⁴⁺ co-doped were successfully synthesized and designed to simultaneously apply to temperature sensing and plant growth LED. With temperature varying from 303 to 523 K, the integrated intensity of Mn⁴⁺ ions (²E_g → ⁴A_2g) markedly decline swifter comparing to Eu³⁺ ions (⁵D₀ → ⁷F₂) due to the thermal quenching effect. It implies that Mn⁴⁺ is susceptive to the temperature in this work. Eu³⁺ exhibits high heat resistance, which can be selected as a calibration parameter for the fluorescence intensity ratio temperature sensor. The maximum relative sensitivity (S_r) values of Ca₂LnSbO₆:1%Eu³⁺, 0.5%Mn⁴⁺ (Ln = La, Y, and Gd) phosphor are estimated as 2.19% K⁻¹ at 443 K, 1.68% K⁻¹ at 503 K, and 1.80% K⁻¹ at 483 K, respectively. They are superior to many recent emerging phosphors. Moreover, upon 365 nm excitation, Ca₂LnSbO₆:1%Eu, 0.5%Mn (Ln = La, Y, Gd, and Lu) phosphors display a wide red emission peaking at 696, 680, 677, and 684 nm, respectively. They come from the overlapped of ²E_g–⁴A_2g of Mn⁴⁺ and ⁵D₀–⁷F₄ transition of Eu³⁺. Their full widths at half maximum are 34, 35, 35, and 29 nm, respectively. They are all perfectly overlapping the absorption curves of chlorophyll a and chlorophyll b, and their fabricated red phosphor-converted light-emitting diode device ulteriorly corroborated the promising applications for plant growth. Markedly, the systematic analysis of their crystal chemistry and site preferentially occupancy is first reported and discussed by the bond valence theory.