Physicochemical study of multicolor BCNO phosphors using a urea combustion method

In this study, the physicochemical properties of BCNO phosphors were investigated based on the color of luminescence to study the luminescence mechanism. Multicolor BCNOs were synthesized by urea combustion methods using boron, carbon, and nitrogen sources consisting of boric acid, PEG 20k, and urea, respectively. The C/B ratio was varied from 0.3 to 2 with temperature variation between 700 and 800 °C, and synthesis time variation at 30 min, 45 min and 60 min. The synthesis process at 775 °C for 30 min with C/B 0.5 and at 750 °C for 45 min with C/B 1 produced samples with three different luminescent colors (violet-blue-yellow and blue-yellow-green respectively), where each color could be separated conventionally. The measurement of luminescence using a PL spectrometer showed photoluminescence at 413-485 nm for the 775 °C sample and 432-511 nm for the 750 °C sample. In the 775 °C sample, PL of sample red-shifted from violet to green, while the 750 °C sample red-shifted from blue to yellow. The result of the x-ray diffraction analysis (XRD) showed the h-BN phase shifting to a red wavelength from blue to yellow sample. The characterization of chemical functional groups using FTIR showed a wide B-N bond and increasingly sharp bonds of C=N, B-C, and B-N-B from yellow to blue sample. The morphology of the three different colors of the samples looked similar, with an irregular structure, but its EDX characterization showed an increasing B/N ratio for the green to blue sample. From these results, it can be concluded that the characteristics of BCNO are influenced by h-BN phase, where an increase of B/N leads to the photoluminescence shifting to blue.