Li Kai, Zhang Yang, Li Xuejiao, Shang Mengmeng, Lian Hongzhou, Lin Jun
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China.
Dalton Trans. 2015 Mar 14;44(10):4683-92. doi: 10.1039/c4dt03720k.
A series of Eu(2+) and Tb(3+) singly-doped and co-doped β-Ca3(PO4)2 phosphors have been synthesized via the high-temperature solid-state reaction method. Thermogravimetric (TG) analysis, fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) patterns and Rietveld refinements, photoluminescence (PL) spectra including temperature-dependent PL and quantum efficiency, and fluorescence decay lifetimes have been used to characterise the as-prepared samples. Under UV excitation, β-Ca3(PO4)2:Eu(2+) presents a broad emission band centered at 415 nm, which can be decomposed into five symmetrical bands peaking at 390, 408, 421, 435 and 511 nm based on the substitution of five kinds of Ca(2+) sites by Eu(2+) ions. β-Ca3(PO4)2:Tb(3+) shows characteristic emission lines under Tb(3+) 4f-5d transition excitation around 223 nm. In β-Ca3(PO4)2:Eu(2+), Tb(3+) phosphors, similar excitation spectra monitored at 415 and 547 nm have been observed, which illustrates the possibility of energy transfer from Eu(2+) to Tb(3+) ions. The variations in the emission spectra and decay lifetimes further demonstrate the existence of energy transfer from Eu(2+) to Tb(3+) ions under UV excitation. The energy transfer mechanism has been confirmed to be dipole-quadrupole, which can be validated via the agreement of critical distances obtained from the concentration quenching (12.11 Å) and spectrum overlap methods (9.9-13.2 Å). The best quantum efficiency can reach 90% for the β-Ca3(PO4)2:0.01Eu(2+), 0.15Tb(3+) sample under 280 nm excitation. These results show that the developed phosphors may possess potential applications in UV-pumped white light-emitting diodes.
通过高温固态反应法合成了一系列铕（Eu(2+)）和铽（Tb(3+)）单掺杂及共掺杂的β - 磷酸钙（β-Ca3(PO4)2）荧光粉。采用热重（TG）分析、傅里叶变换红外（FT-IR）光谱、X射线衍射（XRD）图谱及Rietveld精修、光致发光（PL）光谱（包括温度相关PL和量子效率）以及荧光衰减寿命来表征所制备的样品。在紫外激发下，β-Ca3(PO4)2:Eu(2+)呈现出以415 nm为中心的宽发射带，基于Eu(2+)离子对五种Ca(2+)位点的取代，该发射带可分解为五个对称带，分别在390、408、421、435和511 nm处达到峰值。β-Ca3(PO4)2:Tb(3+)在223 nm左右的Tb(3+) 4f - 5d跃迁激发下显示出特征发射线。在β-Ca3(PO4)2:Eu(2+), Tb(3+)荧光粉中，观察到在415和547 nm处监测到的类似激发光谱，这说明了能量从Eu(2+)转移到Tb(3+)离子的可能性。发射光谱和衰减寿命的变化进一步证明了在紫外激发下存在从Eu(2+)到Tb(3+)离子的能量转移。能量转移机制已被确认为偶极 - 四极，这可以通过从浓度猝灭（12.11 Å）和光谱重叠方法（9.9 - 13.2 Å）获得的临界距离的一致性来验证。在280 nm激发下，β-Ca3(PO4)2:0.01Eu(2+), 0.15Tb(3+)样品的最佳量子效率可达90%。这些结果表明，所开发的荧光粉可能在紫外泵浦白光发光二极管中具有潜在应用。
