The Ba₃Y₄O₉ host matrix with a low cutoff phonon energy of 585 cm⁻¹ is first applied to upconversion (UC) luminescence (UCL) by codoping Er³⁺/Yb³⁺. The new phosphor shows an intense red UC emission which is 6.8-fold and 5.9-fold stronger than that of Y₂O₃ and β-NaYF₄, respectively, under 980 nm GaAs laser diode (LD) excitation at a low density. A broad absorption band centered at 976 nm is observed, meaning a high adaptability to the GaAs LD required in actual applications. The optical thermometry behaviors based on the temperature dependent fluorescence intensity ratios of thermally coupled green UC bands ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 as well as the thermally coupled red UC emission bands originating from the Stark sublevels of ⁴F_9/2 manifold have been explored. The results show that green emissions are suitable for temperatures above 350 K with the maximum sensitivity of 0.00248 K⁻¹ at 563 K and the red emissions are appropriate for temperatures below 350 K with the maximum sensitivity of 0.00371 K⁻¹ at 143 K in our experimental range, indicating their complementary temperature sensing ranges. Moreover, a new method is proposed for evaluating the radiative lifetime of the Er^{3+ 4}F_9/2 state based on the analysis of photoluminescence (PL) spectra and fluorescence decay curves. The radiative lifetime of 879 μs for the red emitting level in Ba₃Y₄O₉ is achieved. Thereby, the emission efficiency of ⁴F_9/2 in the new UCP is a little higher than that in Y₂O₃. Our results imply that Ba₃Y₄O₉:Er³⁺/Yb³⁺ is a promising UCP, which could be applied to wide scope optical thermometry using a dual-color scheme.

中文翻译：

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Er ³⁺ / Yb ³⁺共掺杂磷光体Ba ₃ Y ₄ O _9，具有强烈的红色上转换发射和光学温度感应行为†

首先，通过共掺杂Er ³⁺ / Yb ³⁺，将低截止声子能量为585 cm ^-1的Ba ₃ Y ₄ O ₉主体矩阵应用于上转换（UC）发光（UCL）。新的磷光体显示出强烈的红色发射UC是6.8倍和比是Y的5.9倍更强₂ ö ₃和β-NaYF ₄分别在980 nm下以低密度激发的GaAs激光二极管（LD）激发。观察到以976 ​​nm为中心的宽吸收带，这意味着对实际应用中所需的GaAs LD具有高度的适应性。光学测温行为基于与温度相关的热耦合绿色UC波段² H _11/ ² → ⁴ I _15/2和⁴ S _3/2 → ⁴ I _15/2以及热耦合红色UC发射的荧光强度比源自⁴ F _9/2的Stark子级的频段已经探索了多方面。结果表明，在我们的研究中，绿色发射适合于350 K以上的温度，在563 K下的最大灵敏度为0.00248 K ^-1，红色发射适合于350 K以下的温度，在143 K下的最大灵敏度为0.00371 K ^-1。实验范围，表明它们的互补温度感应范围。此外，基于光致发光（PL）光谱和荧光衰减曲线的分析，提出了一种评估Er ^{3+ 4} F _9/2态的辐射寿命的新方法。Ba ₃ Y ₄ O _9中红色发射能级的辐射寿命为879μs已完成。因此，新UCP中⁴ F _9/2的发射效率比Y ₂ O _3中的发射效率稍高。我们的结果表明，Ba ₃ Y ₄ O ₉：Er ³⁺ / Yb ³⁺是一种很有前途的UCP，可以使用双色方案应用于宽范围的光学测温。