Ln2Sn2O7：Er3+纳米晶的制备及发光性能研究

采用溶胶-凝胶法合成Ln₂Sn₂O₇:Er³⁺(Ln=La,Gd,Y)纳米晶。通过X射线衍射和场发射扫描电子显微镜测试了样品的晶体结构和形貌,同时对样品的上转换发光性能进行了测试。结果表明:在980 nm连续激发光的激发下,样品主要表现为绿光发射。发射中心在528,549 nm的绿光和672 nm处的红光发射分别对应Er³⁺离子的⁴S_3/2→⁴I_15/2、²H_11/2→⁴I_15/2和 ⁴F_9/2→⁴I_15/2跃迁。以La₂Sn₂O₇:Er³⁺纳米晶为例,Er³⁺离子的摩尔分数为7%、退火温度为1 150℃是其制备的最佳条件,此时其各个发射峰的强度最高。对La₂Sn₂O₇:Er³⁺的发光强度与激发功率关系的研究表明,其绿光和红光发射均为双光子过程。激发光吸收和能量转移是La₂Sn₂O₇:Er³⁺纳米晶上转换发光的主要机制。

Preparation and Up-conversion Emissions of Er3+ Doped Ln2Sn2O7 Nanocrystals

Er³⁺ doped Ln₂Sn₂O₇ (Ln=La,Gd,Y) nanocrystals were fabricated by sol-gel method. The crystal structure and morphologies were investigated by XRD and SEM, and the up-conversion spectroscopic properties of the samples were also investigated. Under the excitation of a 980 nm diode laser, the samples mainly emit bright green light. The strong green and red up-conversion emissions which centered at 549, 528, and 672 nm, respectively. They were assigned to the transitions of ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 energy levels of Er³⁺ ions. Taking La₂Sn₂O₇:Er³⁺ nanocrystal for example, the most efficient up-conversion emission can be obtained when the annealing temperature is 1 150℃ and the mole fraction of Er³⁺ is 7%. The dependence of the intensity of up-conversion emissions upon the excitation power of the diode laser suggests that two-photon absorption processes are involved in the green and red up-conversion luminescence. The excited state absorption and energy transfer process are regarded as the main up-conversion emission mechanism of La₂Sn₂O₇:Er³⁺ nanocrystals.