The energy transfer between lanthanide ions (Ln³⁺) and transition metal ions (Cr³⁺) typically leads to luminescence attenuation, which hinders their application in temperature measurement. However, this issue can be effectively addressed by synthesizing polyphase glass-ceramics that separate the Ln³⁺ and Cr³⁺ into different nano-crystals.

In this study, we designed polyhedral glass-ceramics (40SiO₂-20Al₂O₃-15LiF-10Ga₂O₃-0.1TmF₃-0.1ErF₃-0.05Cr₂O₃-1YbF₃-0.5SnO) doped with Ln³⁺/Cr³⁺ (Ln³⁺=Er³⁺/Tm³⁺/Yb³⁺). The up-conversion spectra of Tm³⁺ and Er³⁺ in the temperature range of 313-573 K, as well as the temperature-dependent properties of the emission intensity ratio of ²E and ⁴T₂ and fluorescence lifetime decay of Cr³⁺ were systematically investigated. The results demonstrate that Ln³⁺/Cr³⁺-doped polyphase glass-ceramics exhibit excellent performance as a four-mode fluorescence temperature measurement material.

Ln³⁺/Cr³⁺-doped glass samples were prepared using melt quenching technology, where the raw materials were melted in a lifting furnace at 1 500 ℃ for 1 h. The sample was then poured onto a preheated copper plate to 300 ℃ and shaped by pressing it with another copper plate. Subsequently, the sample was annealed in a Muffle furnace at 450 ℃ for 6 h to obtain precursor glass (PG). Finally, the PG sample underwent heat treatment at 780 ℃ for 2 h to produce glass-ceramics (GC780).

X-ray diffraction apparatus was employed to measure the XRD spectra of these samples. FS-5 fluorescence spectrometer was used to measure various spectra including up-conversion and down-conversion spectra at room temperature, power-dependent up-conversion spectra, temperature-dependent up-conversion and down-conversion spectra, as well as temperature-dependent fluorescence lifetime decay curves. Transmission electron microscopy techniques such as selective electron diffraction and high-power transmission electron microscopy were utilized to examine GC780 samples.

The diffraction peaks observed in the XRD pattern of GC780 exhibit excellent agreement with the standard cards of γ-Ga₂O₃ and β-YF₃ respectively, indicating the successful synthesis of polyphase glass-ceramics containing γ-Ga₂O₃ and β-YF₃ grains. The excitation and emission spectra of Cr³⁺ as well as the up-conversion spectra of Er³⁺ and Tm³⁺ indicate no energy transfer between Cr³⁺ and Er³⁺ or Tm³⁺.

In the variable temperature up-conversion emission spectra of GC780 sample within a temperature range of 313 to 573 K, the emission peak intensity ratio (FIR) I₅₂₂/I₅₄₃ and I₆₉₄/I₄₇₄, which change with temperature, were selected for temperature detection. As the temperature increases from 313 K to 573 K, there is a decrease in relative sensitive (S_R) for I₅₂₂/I₅₄₃ with increasing temperature, reaching a maximum value of 1.03%·K^-1 at 313 K. On the other hand, S_R for I₆₉₄/I₄₇₄ initially increases and then decreases with rising temperature, peaking at a maximum value of 1.45%·K^-1 at 473 K. In the down-conversion temperature-changing spectra (303-543 K) of Cr³⁺ excited at 397 nm, the intensity of the luminescence peaks at 615 nm and 720 nm is used to detect the temperature dependence of FIR(I₆₁₅/I₇₂₀). When the temperature is from 303 K to 543 K, S_R gradually decreases with increasing temperature, and the maximum value of 1.74%·K^-1 appears at 303 K. The relative sensitivity is 0.51%·K^-1 at 496 K when Cr³⁺ down-conversion attenuation curve is used to measure temperature dependence.

Polyphase glass-ceramics doped with β-YF₃ and γ-Ga₂O₃ nano-crystals in Ln³⁺/Cr³⁺ (Ln³⁺=Er³⁺/Tm³⁺/Yb³⁺) have been successfully synthesized by melt quenching method in this work. The up-conversion spectra of GC780 were measured in the temperature range of 313-573 K. The maximum relative sensitivities were 1.03%·K^-1 and 1.45%·K^-1, respectively, by selecting I₅₂₂/I₅₄₃ and I₆₉₄/I₄₇₄ intensity ratios. The ²E→⁴A₂ and ⁴T₂→⁴A₂ emission₂ peaks of Cr³⁺ were used for temperature detection, and the maximum relative sensitivity was 1.74%·K^-1 at 303 K. In addition, the Cr³⁺ down-conversion attenuation curve is used to measure the temperature dependence, and the maximum relative sensitivity is 0.51%·K^-1 at 496 K. The Ln³⁺/Cr³⁺ (Ln³⁺=Er³⁺/Tm³⁺/Yb³⁺) co-doped β-YF₃ and γ-Ga₂O₃ nano-crystals polyphase glass-ceramic is thus indicated to be a highly promising competitive four-mode self-calibration temperature measurement material.