Boltzmann thermometer with broadband emission in Mn4+-Doped β-Ga2O3 crystals.

The luminescence properties of Mn4+-doped β -Ga 2 O 3 are strongly affected by the surrounding crystal field within the [MnO 6 ] octahedral site, which is substitute for Ga Ⅱ site, as determined through the first-principles calculations. The crystal field strength parameters Dq, B, and C are computed, and the Tanabe-Sugano diagram is redrawn for C/B = 6.7. The temperature dependence of the optical spectra is thoroughly examined, revealing the thermal quenching mechanisms involving the thermal activation energy of 2E g and 4T 2g , which are 378 ± 26 cm−1 and 3527 ± 25 cm−1, respectively. In order to further investigate the temperature sensing characteristics, the absolute (S a) and relative (S r) sensitivities are obtained. At 303 K, the S r is determined to be 0.72 %K−1, while S a is estimated to be in the range of 10−2 (below 0.05 K-1) for the Mn4+ doped β -Ga 2 O 3 thermometers. The thermal resolution δT is demonstrated to be below 0.1 K, surpassing that of traditional Nd3+ and Er3+-doped thermometers. Moreover, a linear relationship between the energy separation ΔE of the thermally coupled 2E g -4T 2g energy levels and the crystal field strength Dq is observed in numerous materials. With this consideration, the nature of the thermometer, along with its S a and S r , can be roughly predicted and designed for various operational conditions. • The Mn4+ doped β -Ga 2 O 3 crystals was successfully grown via the optical floating zone method and their luminescence properties was first investigated in detail. • The temperature dependence of luminescence properties was further studied with the thermal quenching activation energy of 2E g and 4T 2g , respectively. • The temperature sensing properties of Mn4+ doped β -Ga 2 O 3 thermometers, whether the relative sensitivities (S r), the absolute sensitivities (S a) or the thermal resolution ΔT, is estimated to be surpassing that of traditional Nd3+ and Er3+-doped thermometers. • A linear relationship between the crystal field strength Dq and the energy separation of the thermally coupled energy levels 2E g -4T 2g was observed, which gives us a broaden idea to predict and design the nature of the thermometer for various conditions. [ABSTRACT FROM AUTHOR]