Irish Valerie B. Maggay

Investigation of luminescence properties and the energy transfer mechanism of Li6Lu(BO3)3:Ce3+, Tb3+ green-emitting phosphors

Li6Lu(BO3)3:Ce3+, Tb3+ phosphor was synthesized via a conventional solid-state method. The phase purity, photoluminescence properties, energy transfer mechanism, thermal stability and chromaticity coordinates were investigated. The absorption spectrum was comprised of broad bands in the UV region and the emission spectrum was consisted of characteristic peaks from both Ce3+ and Tb3+ under UV excitation. The amount of Ce3+ was fixed to 3 mol% while Tb3+ was varied from 20 to 80 mol% and the chromaticity coordinates were tuned from the blue to green region. The energy transfer mechanism between Ce3+ and Tb3+ was attributed to a quadrupole–quadrupole interaction and the critical distance was measured to be 8.12 A. The overall performance of the phosphor was enhanced by the efficient energy transfer between Ce3+ and Tb3+ ions.

Electrochemical properties of novel FeV 2 O 4 as an anode for Na-ion batteries

Spinel based transition metal oxide – FeV2O4 is applied as a novel anode for sodium-ion battery. The electrochemical tests indicate that FeV2O4 is generally controlled by pseudo-capacitive process. Using cost-effective and eco-friendly aqueous based binders, Sodium-Carboxymethylcellulose/Styrene butadiene rubber, a highly stable capacity of ~97 mAh∙g−1 is obtained after 200 cycles. This is attributed to the strong hydrogen bonding of carboxyl and hydroxyl groups indicating superior binding with the active material and current collector which is confirmed by the ex-situ cross-section images of the electrode. Meanwhile, only ~27 mAh∙g−1 is provided by the electrode using poly(vinylidene difluoride) due to severe detachment of the electrode material from the Cu foil after 200 cycles. The obtained results provide an insight into the possible applications of FeV2O4 as an anode material and the use of water-based binders to obtain highly stable electrochemical tests for sodium-ion battery.

Novel Phosphors for UVLEDs

Phosphor is a key component in the recent advances in light-emitting diodes. It converts the light emitted by ultraviolet or blue LEDs into visible light. In the past decade, scientists and researchers have developed various phosphors for general illumination and optical displays, and they continue to develop new phosphors for w-LEDs in order to overcome conventional lighting systems. The phosphors should have strong absorption of the light emitted by the UVLEDs and be able to efficiently downconvert it into longer wavelengths (i.e., visible light). Among the number of developed phosphors, silicate-, borate-, phosphate-, and nitride-based phosphors for have been studied for UVLED applications. This chapter will discuss novel phosphors for UVLEDs according to their chemical compositions and their pertinent applications in white light‒emitting diodes.