# Dual-functional application of Ca2Ta2O7:Bi3+/Eu3+ phosphors in multicolor tunable optical thermometry and WLED

## TL;DR

This paper introduces a new phosphor material that can be used for optical thermometers and white LEDs, with tunable colors and high performance.

## Contribution

The novel contribution is the development of a dual-functional phosphor with tunable optical thermometry and WLED applications.

## Key findings

- The phosphor exhibits tunable color emission from green to reddish-orange via energy transfer.
- The thermometer has high sensitivity and stability up to 510 K.
- A WLED device with a high Ra value of 95.3 was successfully created using the phosphor.

## Abstract

A series of Bi3+/Eu3+ co-doped Ca2Ta2O7 (CTO:Bi3+/Eu3+) phosphors were prepared by high-temperature solid-state method for dual-emission center optical thermometers and white light-emitting diode (WLED) device. By modulating the doping ratio of Bi3+/Eu3+ and utilizing the energy transfer from Bi3+ to Eu3+, the tunable color emission ranging from green to reddish-orange was realized. The designed CTO:0.04Bi3+/Eu3+ optical thermometers exhibit significant thermochromism, superior stability, and repeatability, with maximum sensitivities of Sa = 0.055 K−1 (at 510 K) and Sr = 1.298% K−1 (at 480 K) within the temperature range of 300−510 K, owing to the different thermal quenching behaviors between Bi3+ and Eu3+ ions. These features indicate the potential application prospects of the prepared samples in visualized thermometer or high-temperature safety marking. Furthermore, leveraging the excellent zero-thermal-quenching performance, outstanding acid/alkali resistance, and color stability of CTO:0.04Bi3+/0.16Eu3+ phosphor, a WLED device with a high Ra value of 95.3 has been realized through its combination with commercially available blue and green phosphors, thereby demonstrating the potential application of CTO:0.04Bi3+/0.16Eu3+ in near-UV pumped WLED devices.

The online version contains supplementary material available at 10.1007/s12200-024-00134-2.