植物补光用非晶态La_(2)Ti_(2)O_(7)∶Eu^(3+)荧光粉的燃烧合成及性能

Combustion Synthesis and Performances of Amorphous La_(2)Ti_(2)O_(7)∶Eu^(3+) Phosphor for Plant Growth Lighting

采用燃烧法合成了非晶态La_(2)Ti_(2)O_(7)∶Eu^(3+)荧光粉,利用X射线衍射、扫描电镜、荧光光谱表征了材料的结构、形貌和发光性能,并进一步制成了LED(light-emitting diode)光源,探讨了补光对小麦生长速率和光合色素含量的影响。与固相法合成的晶态La_(2)Ti_(2)O_(7)∶Eu^(3+)相比,非晶态La_(2)Ti_(2)O_(7)∶Eu^(3+)荧光粉中Eu^(3+)离子配位环境的对称性减小,因而显著提高了7F2能级相对于7F1能级的发射强度,使得红光相对橙光成分明显增加,色坐标位于(0.661,0.339),色纯度从90.9%提高为95.9%,适用于植物补光LED。同时,该非晶态荧光粉克服了一般非晶基质中Eu^(3+)发光较弱的问题,荧光内量子效率可高达79.8%,用其制成的LED灯能有效促进小麦的生长,使得叶片中叶绿素和胡萝卜素含量提高了约28%。

Amorphous La_(2)Ti_(2)O_(7)∶Eu^(3+)phosphors were synthesized by the combustion method and characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),and photoluminescence spectra to study the structure,morphology,and luminescent properties.Then it was further applied in wheat growth lighting LEDs(lightemitting diodes)to investigate the illumination effect on growth rate and photosynthesis pigments of wheat.Compared with the crystalline sample synthesized by the solid-state method,the amorphous La_(2)Ti_(2)O_(7)∶Eu^(3+)phosphor can increase the emission intensity of 7F2 energy-level transition relative to 7F1 energy-level from 2.8 to 5.3 by reducing the coordination environment symmetry around Eu^(3+)ions,and the emission peak showed a redshift from 611 to 613 nm.The amorphous La_(2)Ti_(2)O_(7)∶Eu^(3+)phosphor exhibited a color coordinate of(0.661,0.339)and a color purity of 95.9%as compared with 90.9%of the crystalline sample,which is more suitable for applications in plant growth lighting LEDs.The amorphous La_(2)Ti_(2)O_(7)∶Eu^(3+)phosphor overcomes the problem of low luminous efficiency of Eu^(3+)ions in the amorphous host,which achieved a high internal quantum efficiency of 79.8%and an external quantum efficiency of 43.0%.Besides,the emission intensity of the amorphous La_(2)Ti_(2)O_(7)∶Eu^(3+)phosphor at 150℃can maintain 46.3%of that at room temperature.Finally,the as-fabricated LED lamp can accelerate the growth rate of wheat,resulting in an improvement of 28%of the content of chlorophyll and carotene,which shows a potential to be applied in agricultural lighting LEDs.