PHOTOLUMINESCENCE STUDIES OF Eu3+ AND Zn2+ CODOPED CaNb206 PHOSPHORS FOR SOLID STATE LIGHTING APPLICATIONS

Abstract

A novel phosphor Ca0.9-xZn0.1Nb2O6: Eux prepared by using solid state reaction at 1050 oC. The photoluminescence properties are investigated in which the excitation spectrum exhibited a charge transfer band in the UV region centered at 266 nm and a sharp peak corresponding to 7F0-5L6 at 395 nm. Emission properties also measured for these niobate phosphors under the 266 and 395 excitation. A broad emission band and 4f-4f transitions of Eu3+ were observed by exciting at 266 nm. By exciting the samples at 266 nm leads to energy transfer from the excited state of [NbO6]7- to the 5D0 band of Eu3+ via the down-converting energy transfer process. The effect of energy transfer on the emission bands was explained under the excitation 266 nm. The concentration dependence emission properties were measured and the results indicate that the emission intensity increases with Eu3+ concentration up to 2.5 mol%, beyond that concentration the emission intensity decreases due to concentration quenching. The intense peak observed in both the cases could be attributed to 5D0-7F2 transition in Eu3+ ions. In order to evaluate the colorimetric performance of the phosphor, the CIE coordinates for the calcium niobate phosphors were calculated using the emission spectra excited by 266 nm and 395 nm. These results show that blue light emitted for undoped sample and tunable color in the white region and finally red can be obtained by adjusting the Eu3+ concentration. Moreover, the chromaticity coordinates of these phosphors under the excitation of 266 nm are located in the boundary of white-light region. Due to the flexibility of colour tuning of this phosphor, this host will be potential candidate to use in solid state lighting applications.