Upconversion photoluminescence of Er-doped Bi₄Ti₃O₁₂ ceramics enhanced by vacancy clusters revealed by positron annihilation spectroscopy

【摘要】 Doping of rare earth elements into Bi₄Ti₃O₁₂ can significantly enhance the upconversion photoluminescence（UCPL）properties,but its structure-property relationship is still unclear.In this work,Er-doped bismuth titanate Bi_4-xEr_xTi₃O₁₂（x=0,0.1,0.2,0.3,0.4,0.5） ceramics were synthesized via solid-state reaction method.The x-ray diffraction analysis confirmed the orthorhombic crystalline structure of the Bi_4-xEr_xTi₃0₁₂ ceramics without any secondary phases.Experiments and calculations of positron annihilation spectroscopy were carried out to characterize their defect structure.The comparison between the experimental and calculated lifetime revealed that vacancy clusters were the main defects in the ceramics.The increase of the intensity of the second positron lifetime component（I₂） of Bi_3.5Er_0.5Ti₃O₁₂ ceramics indicated the presence of a high concentration of vacancy clusters.The UCPL spectra showed the sudden enhanced UCPL performance in Bi_3.7Er_0.3Ti₃O₁₂ and Bi_3.5Er_0.5Ti₃O₁₂ ceramics,which were consistent with the variation of the second positron lifetime component（I₂）.These results indicate that the enhanced UCPL properties are influenced not only by the concentrations of rare earth ions but also by the concentration of vacancy clusters present within the ceramics.更多还原

【Abstract】 Doping of rare earth elements into Bi₄Ti₃O₁₂ can significantly enhance the upconversion photoluminescence（UCPL）properties,but its structure-property relationship is still unclear.In this work,Er-doped bismuth titanate Bi_4-xEr_xTi₃O₁₂（x=0,0.1,0.2,0.3,0.4,0.5） ceramics were synthesized via solid-state reaction method.The x-ray diffraction analysis confirmed the orthorhombic crystalline structure of the Bi_4-xEr_xTi₃0₁₂ ceramics without any secondary phases.Experiments and calculations of positron annihilation spectroscopy were carried out to characterize their defect structure.The comparison between the experimental and calculated lifetime revealed that vacancy clusters were the main defects in the ceramics.The increase of the intensity of the second positron lifetime component（I₂） of Bi_3.5Er_0.5Ti₃O₁₂ ceramics indicated the presence of a high concentration of vacancy clusters.The UCPL spectra showed the sudden enhanced UCPL performance in Bi_3.7Er_0.3Ti₃O₁₂ and Bi_3.5Er_0.5Ti₃O₁₂ ceramics,which were consistent with the variation of the second positron lifetime component（I₂）.These results indicate that the enhanced UCPL properties are influenced not only by the concentrations of rare earth ions but also by the concentration of vacancy clusters present within the ceramics.更多还原