Sol-gel synthesis of chromium-doped forsterite
Sol-gel synthesis of chromium-doped forsterite
复制标题
溶胶-凝胶法合成铬掺杂镁橄榄石
DOI：
10.1021/cm00028a020
复制
发表时间：
1993
影响因子：
8.6
通讯作者：
Clifford R. Pollock
中科院分区：
文献类型：
--
作者：
D. Park;J. M. Burlitch;R. Geray;R. Dieckmann;D. Barber;Clifford R. Pollock
以镁硅酸盐溶胶为原料，在低温下制备了淡紫色多晶掺铬镁橄榄石粉体。将作为乙酸铬（II）或氧化铬（VI）引入的铬掺杂剂在溶液中组合以最大化均匀性。电子吸收光谱表明，掺杂剂离子，Crm和CrVI，密切结合到硅酸镁网络。在Cr/Si摩尔比为0.04或更低时，干燥的干凝胶在潮湿空气中煅烧至560 ℃后仅形成单相镁橄榄石，并且在800 ℃以上完全结晶。在煅烧过程中使用增湿空气可降低干凝胶的残余碳含量。FTIR光谱表明，掺杂剂占据八面体和四面体的网站。在第一批生长掺铬镁橄榄石单晶的实验中，通过无坩埚浮区法在氧气气氛下熔化和固化多晶粉末来获得粗粒度样品。在室温和典型的近红外发射光谱的宽ESR峰的观察表明，在熔体生长的样品中的Cr 4 +/Cr 3+的比例高于商业单晶，在更还原的气氛下生长。
Pale purple, polycrystalline, chromium-doped forsterite powder was prepared at low temperature from a magnesium silicate sol. The chromium dopant, introduced as either chromium (II) acetate or chromium (VI) oxide, was combined in solution to maximize homogeneity. Electronic absorption spectroscopy indicated dopant ions, Crm and CrVI, were intimately bound to the magnesium silicate network. At a Cr/Si mole ratio of 0.04 or less, the dried xerogel formed only a single phase, forsterite, after calcination in humid air to 560 C, and was fully crystalline above 800 0 C. The residual carbon content of the xerogel was decreased by the use of humidified air during calcination. FTIR spectroscopy indicated that the dopant occupied both octahedral and tetrahedral sites. In the first attemptsto grow single crystals of chromium-doped forsterite, coarse-grained samples were obtained by melting and solidification of the polycrystalline powder under an oxygen atmosphere by the crucible-free, floating zone method. Observation of a broad ESR peak for Cr4+ at room temperature and of typical near IR emission spectra indicated that the Cr4+/Cr3+ ratio in the melt grown samples was higher than that of commercial single crystals, grown under a more reducing atmosphere.