Ce,Pr-Coactivated Phosphor for 185 nm UVB Emission
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Solution Overview
Problem
Conventional Sr(Al,Mg)12O19:Ce phosphors used in suntan lamps are poorly excited by 185 nm radiation, leading to wasted energy and inefficient UVB emission.
Innovation Solution
Incorporating a praseodymium coactivator into the strontium magnesium aluminate phosphor, creating a Ce,Pr-coactivated phosphor that enhances sensitivity to 185 nm radiation while maintaining response to 254 nm radiation, allowing for increased UVB emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional Sr(Al,Mg)12O19:Ce phosphor is used in suntan lamps, then UVB emission is achieved, but excitation efficiency by 185 nm radiation is poor leading to energy waste
Solution Approach 1:
The patent applies composite materials by combining two activators (cerium and praseodymium) within the same phosphor host structure. The Ce,Pr-coactivated Sr(Al,Mg)12O19 phosphor creates a composite system where Pr3+ absorbs 185 nm radiation and transfers energy to Ce3+ for UVB emission, resolving the energy waste problem while maintaining productivity
Solution Approach 2:
The patent changes the chemical composition parameters of the phosphor by introducing praseodymium as a coactivator with specific concentration ranges (0.001-0.05 moles Pr/mole phosphor). This parameter modification enables the phosphor to respond to 185 nm radiation while maintaining 254 nm response, eliminating energy waste and improving UVB emission efficiency
2Productivity
If quantity of Sr(Al,Mg)12O19:Ce phosphor is increased to improve UVB emission, then UVB output increases, but overall UV light output (UVA and UVB) is reduced due to displacement of UVA-emitting phosphors
Solution Approach 1:
The Ce,Pr-coactivated phosphor acts as a composite material that responds to both 185 nm and 254 nm radiation, enabling dual excitation pathways. This allows the phosphor to generate UVB emission while coexisting with UVA-emitting phosphors in the blend, thereby increasing overall UV light output without sacrificing UVB productivity
Solution Approach 2:
The modified phosphor achieves multi-functionality by being excited by both 185 nm and 254 nm radiation sources. This universal response capability allows a single phosphor component to contribute to both UVB emission and overall UV output, eliminating the need to increase phosphor quantity at the expense of UVA phosphors
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 Ce,Pr-coactivated phosphor achieves improved UVB emission under both 185 nm and 254 nm excitation, enabling reduced phosphor quantities in suntan lamps with increased overall UV light output and tanning efficiency.
Implementation Method 1
Suntan lamps are based on the conventional low-pressure mercury discharge prevalent in fluorescent lighting. The primary UV excitation energy emitted by a low-pressure mercury discharge is at 254 nm. However, a sizeable portion of the total UV radiation is also emitted at 185 nm.
Implementation Method 2
The cerium and praseodymium coactivated strontium magnesium aluminate phosphor of this invention may be represented by the formula, Sr(Al,Mg)12O19:Ce,Pr. When both Pr and Ce are used as co-activators in this phosphor, the phosphor is excited by both 185 nm and 254 nm radiation and emits primarily in the UVB region.
Implementation Method 3
When both Pr and Ce are used as co-activators in this phosphor, the phosphor is excited by both 185 nm and 254 nm radiation and emits primarily in the UVB region. Presumably, the excited Pr3+ sites transfer nearly all of their energy to the Ce3+ sites, where it is emitted as UVB radiation at about 306 nm.
Data Source
AI summary
A Sr(Al,Mg)12O19:Ce,Pr phosphor is described wherein the phosphor has an increased sensitivity to excitation by 185 nm radiation compared to a Sr(Al,Mg)12O19:Ce phosphor. The Ce,Pr-coativated strontium magnesium aluminate phosphor emits ultraviolet (UV) radiation at about 306 nm in the UVB region. Suntan lamps made with this phosphor exhibit improved performance over lamps made with a commercial Sr(Al,Mg)12O19:Ce phosphor.