Strong green-light emitting Tb3+ doped tetragonal ZrO2 nanophosphors stabilized by Ba2+ ions

For a balanced white light in a phosphor down-conversion LED, a proper combination of blue, green and red emission is desirable for better colour rendering capability as desired in general illumination. Since ZrO2 has 3 polymorphism, Ba2+ ion was used to stabilize it in the tetragonal phase. A chemical bath deposition technique was employed in the synthesis procedure. X-ray diffraction measurements show pure tetragonal phase at all Tb3+ concentrations. FTIR, Raman spectroscopy, TEM and SAED analyses all confirmed the tetragonal phase of zirconia without impurity phases. Diffuse reflectance spectroscopy show the formation of both host and intraconfigurational line absorption of Tb3+ ion. Photoluminescence emissions (PL) at room and low (77 K) temperatures gave strong green emission emanating from the 5D4 - 7F5 transition. However, PL intensity was quenched at higher concentrations due to dipole - dipole interaction and energy transfer between adjacent ions. Temperature dependence PL show quenching of emission intensity as the temperature increases due to the dominance of nonradiative transitions at higher temperatures. The Ba-ZrO2: Tb3+ nanophosphors were observed to be very stable, losing half of its emission intensity at 350 °C. The CIE coordinate values of the synthesized green phosphor are comparable to the commercial green light emitting phosphors and with a purity of 83%. Hence this phosphor can be used as a green emitter for different device applications, especially in high power white LEDs.