Abstract
Phosphor coated diodes are critical to the lighting industry. Rare-earth doped fluoride phosphors are characterized in this work. Spectroscopy and lifetime measurements of CaF2: Dy3+, LaF3: Eu3+ and Tb3+-doped LaF3 and CaF2 crystals were performed by irradiating the samples with 405 and 375 nm diode lasers. Chromaticity diagrams are developed from spectral measurements. Dy3+-doped CaF2 revealed bright white light emission having peaks at 492, 570 and 654 nm. The measured color coordinates are x = 0.322 and y = 0.340 for Dy3+-doped CaF2 and these values are close to those of sunlight and the coordinated color temperature is 6147 K, under 405 m laser excitation. Eu3+-doped LaF3 revealed twenty emission peaks in the visible wavelength region. The color coordinates measured for LaF3: Eu3+ are x = 0.283 and y = 0.293 under 405 nm diode laser excitation and the color temperature is 9557 K. Eu3+-doped LaF3 provides cool white-light, under 405 nm diode laser excitation. Tb3+-doped fluoride crystals revealed bright white light under low power diode laser excitation. The measured color coordinates for Tb3+-doped CaF2 are x = 0.329 and y = 0.558 and the color temperature is 7713 K. The color coordinates for LaF3: Tb3+ are x = 0.342 and y = 0.365 and the coordinated color temperature is 5370 K. These values are close to those of sunlight.
Highlights
IntroductionSome of the rare-earth ions possess numerous energy levels and emit in the visible and infrared wavelength regions
About 20 percent of the electricity supplied to homes is used in lighting
The color coordinates measured for LaF3: Eu3+ are x = 0.283 and y = 0.293 under 405 nm diode laser excitation and the color temperature is 9557 K
Summary
Some of the rare-earth ions possess numerous energy levels and emit in the visible and infrared wavelength regions. Depending on the energy level structure, a rare-earth ion may absorb certain discrete lasers wavelengths. Because of these characteristic spectral features, materials embedded with single, double or triple dopants, emit different colors. Rare-earth ion doped materials were investigated because of their applications in the laser development, luminescent devices, optical refrigeration, optical memories, temperature measurement and others [12] [13] [14] [15] [16]. Rare-earth doped materials are being investigated for possible applications in solid-state lighting [19]-[24]. The cut-off phonon frequency of LaF3 and CaF2 crystals are 360 and 380 cm−1 respectively
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