Abstract
This work reports the structural, morphological and luminescent properties of CaCO3:Eu3+ phosphors synthesized by a precipitation method. Those phosphors were made under different conditions such as: mole ratio for Ca:CO3 (1:1, 1:2 and 1:3), pH (from 7 to 11), temperature (from 25 to 75 °C) and Eu3+ concentration (from 1 to 5 at.%). We used a Taguchis’ design (orthogonal L9 array) to find the optimum conditions that allow the synthesis of CaCO3:Eu3+ phosphors with the highest red emission intensity. After this, only 9 samples were synthesized. According to the X-ray diffraction patterns, all the samples presented a mixture of vaterite and calcite phases. Different morphologies were also observed by scanning electron microscopy such as porous microspheres, stacked pillars, microbelts or coalesced particles. We also measured the photoluminescence (PL) spectra for these 9 samples and calculated their integrated PL intensity. Those values were used as input in the ANOVA analysis, which was employed to find the critical parameters that affect the emission intensity of the samples. As a result, we found that the temperature and the mole ratio of Ca:CO3 are the most influential factors on the luminescent properties. We also employed the McCamy formula to calculate the correlated color temperature (CCT) and obtained values in the range of 1763–2797 K, which correspond to warm lighting sources. Moreover, the phosphor with the highest orange/red emission intensity presented a color purity of 96.66%, which is close to that used by the National Television Standard Committee (NTSC). Hence, the results presented here demonstrated that the CaCO3:Eu3+ phosphors could be used as a red-emitting component in White LEDs excited with UV chips.
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