Chemical route for synthesis of β-SiAlON:Eu2+ phosphors combining polymer-derived ceramics route with non-hydrolytic sol-gel chemistry

We report the synthesis of beta-SiAlON:Eu2+ phosphors from novel single source precursors in which strictly controlled chemical composition is established at molecular scale. The two-step synthesis occurs by the chemical modification of perhydropolysilazane (PHPS) with Al(OCH(CH3)(2))(3) and AlCl3 in xylene at room temperature to 140 degrees C to introduce Al in the PHPS network while controlling the oxygen content followed by the reaction of EuCl2 with the Al-modified PHPS upon heat-treatment. Gas chromatography-mass spectrometry and thermogravimetry-mass spectrometry analyses revealed that PHPS reacted with Al(OCH(CH3)(2))(3) and AlCl3 via the formation of Al-N bonds. Moreover, AlCl3 reacted with nitrogen-bonded Al alkoxide residue to release 2-chloropropane in an analogy to the non-hydrolytic sol-gel reaction between metal alkoxide and metal chloride. Subsequently, AlCl3 acted as a Lewis acid catalyst to promote the Friedel-Craft alkylation between xylene solvent and the 2-chloropropane formed in-situ to afford dimethylcumene. On the other hand, EuCl2 reacted with silylamino moiety to form Eu-N bonds at around 850 degrees C. beta-SiAION:Eu2+ phosphors were successfully synthesized by pyrolysis of the precursors under flowing N-2 or NH3 at 1000 degrees C, followed by heat treatment at 1800 degrees C for 1 h under a N-2 gas pressure at 980 kPa. The polymer-derived beta-SiAION:Eu2+ (z = 0.55, Eu2+ 0.37 at%) exhibited green emission under excitation at 410 or 460 nm, and the green emission intensity under the excitation at 410 nm was found to be increased by reducing the carbon and chlorine impurities through the polymer-derived ceramics route investigated in this study. [GRAPHICS] .

Automated summary

In this study, we report the synthesis of β-SiAlON:Eu2+ phosphors using novel single source precursors. By establishing strict control over the chemical composition at the molecular scale, we were able to successfully synthesize β-SiAlON:Eu2+ phosphors that exhibit green emission properties.