Synthesis and upconversion color Tunability luminescence of K5Yb(MoO4)4 phosphor doped with Er3+and optical temperature sensing applications

A series of double molybdates with palmierite-related structure phosphors K₅Yb_1-x (MoO₄)₄:xEr³⁺ were synthesized by a solid-state method. It has been demonstrated that the K₅Yb_1-x (MoO₄)₄: xEr³⁺ phosphors are capable of exhibiting the characteristic green and red UC emission of Er³⁺ ions with excitation at 980 nm. Moreover, the green light emission is far more than the red light emission, so that the sample emits a powerful green light, which belongs to the two-photon absorption process. The upconversion efficiency is peaked when the content of Er³⁺ ions is 10 mol %. The optical thermometry properties of phosphors were explored by observing that the green UC emission intensity is temperature dependent. The maximum sensor sensitivity of the studied phosphor was discovered to be about 1.61%K⁻¹ at the optimum doping concentration. And the phosphor is demonstrated to have high thermal stability by temperature cycling test. Eventually, a green light-emitting diode device was realized by using synthesized particles and a 980 nm near-infrared chip, which can emit a more obvious green light when the voltage reaches 1.80 V and the current can reach 800 mA, thus confirming its applicability in solid-state lighting. And the LED devices have been tested for life stability with little or no light degradation. These properties make the phosphors not only suitable for non-contact optical temperature measurement, but also able to be applied to solid state lighting.