Tb-Activated Phosphor Broad Emission Band via Valence Control
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Solution Overview
Problem
Conventional phosphors using Terbium (Tb) ions as activators suffer from poor luminous efficiency and lack of adjustability due to narrow emission bands, limiting their applicability in light-emitting applications.
Innovation Solution
A phosphor with the formula TxEySizNrTbaLbMc, where T is Mg, Ca, Sr, or Ba, and Tb is used as a luminescence center, exhibiting an emission band with a full width at half maximum (FWHM) greater than 50 nm, achieved by mixing Tb-containing, Si-containing, and IIA metal-containing compounds and calcining them in a carbon-containing atmosphere, which reduces the valence of Tb ions to less than 3+, resulting in a broad emission band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional phosphors use Terbium (Tb) ions as activators, then the phosphor structure is simple and easy to manufacture, but the luminous efficiency is poor and the emission band is narrow
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor host lattice by introducing specific metal elements (Mg, Ca, Sr, Ba) and controlling the ratio of Al to Si and O to N. This parameter optimization broadens the emission band of Tb ions and improves luminous efficiency while maintaining manufacturability
Solution Approach 2:
The patent creates a composite phosphor material with a complex host lattice structure containing multiple metal elements (TxEySizNrTbaLbMc). This composite structure provides multiple energy transfer pathways to Tb activators, enhancing luminous efficiency and broadening emission bands
2Ease of manufacture
If conventional phosphors use Terbium (Tb) ions as activators, then the phosphor structure is simple, but the emission band is narrow and color adjustability is poor
Solution Approach 1:
The patent systematically varies the composition parameters (x, y, z, r, a, b, c) of the host lattice to tune the emission characteristics. By adjusting the ratios of different metal elements and anions, the emission band can be broadened and its peak position shifted, enabling color temperature adjustment from warm white to cool white
Solution Approach 2:
The patent develops a universal phosphor system TxEySizNrTbaLbMc that can achieve multiple emission colors and broad emission bands through compositional variation. This single system structure serves multiple lighting applications, replacing the need for different phosphor formulations
3Reliability
If the phosphor uses a broad emission band with FWHM greater than 50 nm, then luminous efficiency and color adjustability are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent uses ball milling to pre-mix the raw materials in precise ratios before calcination. This preliminary homogeneous mixing ensures complete reactions during calcination, simplifying the overall manufacturing process despite the complex composition, and consistently produces phosphors with broad emission bands
Solution Approach 2:
The patent optimizes calcination parameters (temperature, atmosphere, time) to achieve complete formation of the complex host lattice structure in a single step. By controlling the calcination atmosphere (reducing or neutral) and temperature (900-1100°C), the complex composition transforms into a stable phase structure that naturally provides broad emission bands
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The phosphor achieves improved luminous efficiency and color adjustability with a broad emission band, overcoming the limitations of conventional phosphors, and demonstrates excellent thermal, chemical stability, and non-toxicity, making it suitable for industrial applications.
Implementation Method 1
an inorganic phosphor generates a fluorescent light through electron transition. When the phosphor is excited by the light, the electrons in the phosphor are excited to the excited state of the high energy level and then the electrons return to the original low energy level state. At this time, the energy is radiated in the form of light.
Implementation Method 2
calcining them in a carbon-containing atmosphere, which reduces the valence of Tb ions to less than 3+, resulting in a broad emission band
Data Source
AI summary
A phosphor having a formula of TxEySizNrTbaLbMc is provided, in which T is Mg, Ca, Sr or Ba; E is Mg, Ca, Ba, Ti, Cu, Zn, B, Al, In, Sn, Sb, Bi, Ga, Y, La or Lu; L is Li, Na or K; M is Ce, Pr, Nd, Pm, Sm, Gd, Dy, Ho, Er, Tm, Yb or Mn; and 1.4≤x≤2.6, 0≤y≤0.5, 4.3≤z≤5.6, 7.4≤r≤9, 0.01≤a≤0.5, 0≤b≤0.5, 0≤c≤0.5, in which Tb ion is used as a luminescence center, and valence of the Tb ion is lower than 3+, and the phosphor is excited by an excitation light and has an emission band with a full width at half maximum greater than 50 nm. A method of forming the phosphor is also provided.