In this study, the upconversion (UC) emissions of Er³⁺ and Yb³⁺ co-doped SrZrO₃ nanocrystals (NCs) were investigated in terms of the thermal annealing temperature and concentration of Er³⁺ ions and compared with the emissions under a near-ultraviolet (near-UV) excitation. The NCs were synthesized by the combustion method, and the as-synthesized NCs were post-annealed at high temperatures. The X-ray diffraction patterns revealed that the grain sizes and crystallinity degrees of the samples increased with increasing annealing temperatures. The photoluminescence spectra of our samples exhibited strong green and very weak red emissions with the near-UV excitation, originating from the f-f transitions in the Er³⁺ ions. Interestingly, under near-infrared (near-IR) excitation, we identified sizable visible emissions at 525, 547, and 660 nm in our NCs, which indicated that the UC process successfully occurred in our NCs. These UC emissions were maximized in the NCs with an Er³⁺ concentration of 0.02 and thermal annealing at 1000 °C. We found that the intensity ratios of red to green emissions increased with increasing annealing temperatures. We discussed the differences in the emissions between near-UV and near-IR excitations.

中文翻译：

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近红外和近紫外激发下Er 3+和Yb 3+共掺杂的SrZrO 3纳米晶体的发射

在这项研究中，从热退火温度和Er ³⁺离子浓度的角度研究了Er ³⁺和Yb ³⁺共掺杂SrZrO ₃纳米晶体（NC）的上转换（UC）发射，并将其与近紫外线（近紫外线）激发。NCs通过燃烧方法合成，合成后的NCs在高温下进行后退火。X射线衍射图表明，样品的晶粒尺寸和结晶度随着退火温度的升高而增加。我们的样品的光致发光光谱在近紫外激发下表现出强绿色和非常弱的红色发射，这是由于Er ^3+中的ff跃迁引起的离子。有趣的是，在近红外（近红外）激发下，我们在我们的NC中确定了在525、547和660 nm处可见的可见光发射，这表明UC过程成功地发生在我们的NC中。这些UC排放物在Er ³⁺浓度为0.02且在1000°C的温度下进行退火时在NC中得到最大化。我们发现，红色与绿色发射的强度比随退火温度的升高而增加。我们讨论了近紫外和近红外激发之间的发射差异。