Alkaline Gallate Phosphors for Persistent Near-Infrared Emission
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Solution Overview
Problem
Current long-persistent phosphors are limited to the visible spectrum, with no available options in the infrared or near-infrared region, which is desirable for military and security applications requiring invisible emission detectable by specific devices, stability in outdoor environments, and long-lasting performance without recharging.
Innovation Solution
Development of alkaline gallate phosphors doped with Cr3+ or Ni2+ ions, capable of emitting in the near-infrared spectrum with persistence times up to 200 hours, activated by solar radiation, UV lamps, or LED light, and stable in various environmental conditions including water, enabling their use in paints and coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If visible spectrum phosphors are used, then persistence time can be extended to 200 hours, but the emission wavelength is limited to visible region which cannot meet infrared detection requirements
Solution Approach 1:
The patent changes the emission wavelength parameter by selecting specific activator ions (Cr3+, Ni2+) that emit in the infrared region while maintaining the gallate host matrix structure. This allows the phosphor to achieve both long persistence time and infrared emission capability simultaneously.
Solution Approach 2:
The patent creates a composite phosphor material by combining the gallate host matrix with specific activator ions (Cr3+, Ni2+) and co-activators. This composite structure enables the material to exhibit both long-persistent phosphorescence and infrared emission properties that neither component alone could achieve.
2Reliability
If alkaline earth aluminates are used, then chemical stability improves, but hydrolysis reaction occurs quickly when contacting moisture and water
Solution Approach 1:
The patent changes the chemical composition by using gallate-based materials instead of alkaline earth aluminates. The gallate structure inherently resists hydrolysis better than aluminate structures, allowing the phosphor to maintain stability in moist and aqueous environments without rapid decomposition.
3Ease of manufacture
If sulfide phosphors are used, then ease of manufacture is maintained, but persistence duration is limited to three hours and instability occurs when ultraviolet light and moisture coexist
Solution Approach 1:
The patent develops a composite phosphor system using gallate host matrix with specific activator ions (Cr3+, Ni2+) and co-activators. This composite structure achieves both long persistence duration (up to 200 hours) and stability in UV-light and moisture conditions, overcoming the limitations of simple sulfide 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 phosphors provide long-lasting near-infrared emission up to 200 hours, are chemically stable in outdoor environments, and can be quickly charged, making them suitable for military, security, and forensic applications.
Implementation Method 1
The phosphors can be activated by solar radiation, UV lamps, or LED light... achieve long-lasting near-infrared emission
Implementation Method 2
Phosphorescence is a phenomenon that the light emitted by a phosphor lasts after stoppage of excitation for duration of time sufficient for light to be perceived by the eye... In persistent phosphors, two kinds of active centers are involved: emitters and traps
Data Source
AI summary
Phosphors based on doping of an activator (an emitter) into a host matrix are disclosed herein. Such phosphors include alkaline gallate phosphors doped with Cr3+ or Ni2+ ions, which in some embodiments can exhibit persistent infrared phosphorescence for as long as 200 hours. Such phosphors can be used, for example, as components of a luminescent paint.