Sol−Gel Syntheses and Spectroscopic Characterization of Chromium-Doped Silicates and Germanates
Sol−Gel Syntheses and Spectroscopic Characterization of Chromium-Doped Silicates and Germanates
复制标题
铬掺杂硅酸盐和锗酸盐的溶胶凝胶合成及光谱表征
DOI：
10.1021/cm990730
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发表时间：
2000
影响因子：
8.6
通讯作者：
K. Miyano
中科院分区：
文献类型：
--
作者：
P. Devi;H. Gafney;V. Petričević;R. Alfano;D. He;K. Miyano
为了避免高温处理技术遇到的技术困难，人们研究了低温溶胶-凝胶法，作为获得掺铬橄榄石、镁硅酸镁以及结构类似物Ca2SiO4和Ca2GeO4的途径。凝胶形成透明、浅色的凝胶，加热到850℃时转化为微晶陶瓷粉末。最初掺入CrCl3.6H(2)O(0.01-1%)，转化为陶瓷时伴随着铬的配位和氧化态的变化。与尺寸考虑一致的是，EPR、EXAFS和XANES数据表明，在Ca2SiO4和Ca2GeO4中，铬主要以四面体配位的Cr4+存在，在Cr-Mg2SiO4中，铬主要以八面体配位的Cr3+和四面体配位的Cr4+的混合物形式存在。可见和近红外电子吸收和发射光谱反映了材料的组成，通过对随机取向微晶陶瓷的吸收进行比较，发现其吸收带的位置和形状与镁橄榄石单晶的偏振吸收有惊人的相似之处
To avoid the technical difficulties encountered with high-temperature processing techniques, low-temperature sol-gel processes have been examined as routes to the Cr-doped olivine, Mg2SiO4, and the structural analogues Ca2SiO4 and Ca2GeO4. Gelation yields transparent, lightly colored gels that are converted to microcrystalline ceramic powders on heating to 850 degrees C. Initially doped with CrCl3.6H(2)O (0.01-1%), conversion to the ceramic is accompanied by changes in the coordination and oxidation state of the chromium. Consistent with size considerations, EPR, EXAFS, and XANES data indicate chromium exists principally as tetrahedrally coordinated Cr4+ in Ca2SiO4 and Ca2GeO4, and as a mixture of octahedrally coordinated Cr3+ and tetrahedrally coordinated Cr4+ in Cr-Mg2SiO4. Visible and near-IR electronic absorption and emission spectra reflect the composition of the material, and a comparison of the absorption of randomly oriented microcrystalline ceramics shows a surprising similarity in both band position and shape to polarized absorptions of forsterite single crystals