Tm^(3+),Yb^(3+)共掺Bi_(2)WO_(6)上转换发光材料的制备及其温度传感性质

Preparation and temperature sensing properties of Tm^(3+),Yb^(3+)co-doped Bi_(2)WO_(6) upconversion luminescent materials

用高温固相法制备了不同浓度的Tm^(3+)和Yb^(3+)共掺杂Bi_(2)WO_(6)上转换发光材料.对合成粉末的微结构、上转换发射光谱,以及材料的光学温度传感性质进行了表征和分析.X射线衍射谱结果显示,Tm^(3+)和Yb^(3+)离子的掺杂基本不影响Bi_(2)WO_(6)基质材料的正交晶系结构.在980 nm激发下,Tm^(3+)和Yb^(3+)掺杂摩尔分数分别是1%和6%时获得样品中Tm^(3+)发射强度最大.随激发泵浦功率从199 mW增加到400 mW,1%Tm^(3+),6%Yb^(3+):Bi_(2)WO_(6)样品中Tm^(3+)的4个发射峰强度均增强.199—400 mW激发功率下,样品光强I和激发功率Pn呈现线性关系.计算该范围激发泵浦功率和Tm^(3+)发射强度的关系,得到Tm^(3+)的4个发射峰478,650,685和705 nm分别对应n值为1.01,1.34,1.77和1.75,这表明以上发射峰均源于双光子吸收.980 nm激发(功率379 mW)下,当温度从298 K升高到573 K时,1%Tm^(3+),6%Yb^(3+):Bi_(2)WO_(6)样品中Tm^(3+)的热耦合能级对(^(3)F_(3),^(3)F_(2))产生705 nm和685 nm处发射强度分别增加了28.4倍和31.6倍.拟合样品中Tm^(3+)的热耦合能级对(3F3,3F2)的荧光强度比与温度的关系,计算得到在298 K时,样品最大绝对测温灵敏度为0.00254 K^(-1),最大相对测温灵敏度为0.00144 K–1.同样条件下,拟合非热耦合能级对(3F3,1G4)产生的705 nm和650 nm荧光强度比与温度关系,计算得到在573 K时,最大绝对测温灵敏度为0.167 K^(-1).298 K时最大相对测温灵敏度为0.0378 K^(-1),比热耦合能级(3F_(3),3F_(2))表征温度的相对最大测温灵敏度Sr提高了26倍.

Tm^(3+)and Yb^(3+),with different concentrations,co-doped Bi_(2)WO_(6)up-conversion luminescence materials are prepared by high temperature solid state method.The microstructure,upconversion emission spectra,and optical temperature sensing properties of the synthesized powders are characterized and analyzed.The X-ray diffraction results show that the doping of Tm^(3+)and Yb^(3+)ions has little effect on the orthorhombic structure of Bi_(2)WO_(6)matrix material.Under the 980 nm excitation,the maximum emission intensity of Tm^(3+)ions is obtained when the doping concentration of Tm^(3+)and Yb^(3+)are 1%and 6%,respectively.The intensities of four emission peaks of Tm^(3+)in 1%Tm^(3+),6%Yb^(3+):Bi_(2)WO_(6)sample increase with the excitation pump power increasing from 199 to 400 mW.With the excitation power of 199-400 mW,the sample light intensity I and the excitation power Pn show a linear relationship.The relationship between the excitation pump power and the emission intensity of Tm^(3+)in this range is investigated.The four emission peaks of Tm^(3+)at 478,650,685 and 705 nm correspond to the n values of 1.01,1.34,1.77 and 1.75,respectively,indicating that the above emission peaks are derived from two-photon absorption.Under 980 nm excitation(power 379 mW),when the temperature increases from 298 to 573 K,the thermal coupling energy levels of Tm^(3+)in 1%Tm^(3+),6%Yb^(3+):Bi_(2)WO_(6)samples produce 705 and 685 nm emission whose intensities are increased by 28.4 times and 31.6 times,respectively.The relationship between the fluorescence intensity ratio of the thermal coupling energy levels(3F_(3),3F_(2))of Tm^(3+)in the sample and the temperature is fitted.The maximum absolute temperature sensitivity of the sample is 0.00254 K^(-1) at 298 K,and the maximum relative temperature sensitivity is 0.00144 K^(-1).Under the same conditions,the relationship between the fluorescence intensity ratio of 705 and 650 nm produced by the non-thermal coupling energy level pair(3F_(3),1G4)and the temperature is fitted,and the maximum absolute temperature sensitivity is calculated to be 0.167 K-1 at 573 K.The maximum relative temperature sensitivity is 0.0378 K-1 at 298 K,which is 26 times higher than the relative maximum temperature sensitivity Sr of the thermal coupling level(^(3)F_(3),^(3)F_(2)).