Chromium‐Doped Forsterite Nanoparticle Synthesis by Flame Spray Pyrolysis

Synthesis of chromium‐doped forsterite (Mg 2 SiO 4 :Cr) nanoparticles by flame spray pyrolysis (FSP) was investigated. The morphology, crystalline phase, and photoluminescence of the products were evaluated. Crystalline Mg 2 SiO 4 :Cr nanoparticles of several 10 nm in diameter were obtained, although a small amount of the submicrometer‐sized particles and the unreacted MgO phase existed. The product powder showed electron‐spin resonance signals from Cr 4+ and photoluminescence typical for Cr 4+ in Mg 2 SiO 4 , suggesting that a part of the Cr 4+ ions were incorporated into Si 4+ sites by FSP. On the other hand, the effects of excess SiO 2 addition on the structural and optical characteristics of Mg 2 SiO 4 :Cr were examined. Addition of excess SiO 2 up to 20 mol% did not influence these characteristics of the products. Further addition of excess SiO 2 (60–100 mol%) enhanced the formation of the amorphous phase and resulted in the emission from Cr 3+ in the amorphous phase in addition to an emission from Cr 4+ in Mg 2 SiO 4 .