Thermally stable Na2ZrO3: Eu3+ phosphors for UV excited tricolor white LEDs

Abstract

Researches are going on to promote a highly thermally stable and efficient phosphor material for the red component of the tri-color white LEDs. Herein, Eu3+ activated Na2ZrO3 phosphors were designed through the traditional high temperature solid state reaction method. The structural studies such as crystallinity, phase purity and surface morphology of the prepared samples were examined from the powder XRD and FE-SEM techniques. The photoluminescence study illustrates that the phosphor can be excited through the charge transfer band and the characteristic excitation wavelength of Eu3+ ions. The emission spectra present pure red emission, resulting from the prominent peak at 608 nm ascribe to the 5D0 → 7F2 transition of Eu3+ ions. Temperature dependent PL and lifetime measurement from 300 K to 475 K with an interval of 25 K were employed to get a deeper insight into the thermal stability of the phosphor. The emission intensity goes on decreasing with an increase in temperature. The activation energy of thermal quenching estimated from the Arrhenius plot is found to be 0.195 eV. Almost 60% of the initial intensity at room temperature is still maintained above 200 °C and the CIE coordinates also remain stable at the higher temperature. The average lifetime of the excited state of Eu3+ ions varied from 0.74 ms to 0.71 ms within the observed temperature range. The above results point out that the aforementioned sample shows good thermal stability and it can be applied as the red emitting phosphor for wLED, operated in the high temperature region.