Redox behavior of VIB transition metal ions in rutile TiO2 solid solutions:: An XRD and EPR study

被引:15
作者
Cordischi, D
Gazzoli, D
Occhiuzzi, M
Valigi, M
机构
[1] Univ Roma La Sapienza, Dipartimento Chim, CNR, Ctr SACSO, I-00185 Rome, Italy
[2] Univ Roma Tre, Dipartimento Ingn Meccan & Ind, I-00146 Rome, Italy
关键词
EPR; solid solutions; CrO2-TiO2; MoO2-TiO2; WO2-TiO2;
D O I
10.1006/jssc.2000.8698
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
CrO2-TiO2 (TC), MoO2-TiO2 (TMo), and WO2-TiO2 (TW), prepared by heating in vacuo at 1173-1273 K mixtures of MO2 (M = Cr, Mo, or W) and TiO2, were characterized by XRD and EPR, The transition metal ions were incorporated as isolated and clustered Cr-III, Mo-IV, and W-IV and a small fraction as isolated Mo-V and W-V in substitutional sites. After heating in air or in O-2 up to 1273 K, in TC no isolated Cr-V formed, whereas in TMo and TW, M-IV was oxidized to M-V and M-VI, and MO3 was segregated. The oxidation started at 673 K and gave isolated substitutional MoV and isolated interstitial and substitutional WV. After heating in H-2 up to 1073 K, TMo and TW reduction process differed: Mo-IV gave isolated and clustered Mo-III, and Mo-IV-Mo-IV pairs gave Mo-2(7+) species; W-IV was not reduced to W-III; and temperatures > 900 K caused the segregation of metallic molybdenum and tungsten, (C) 2000 Academic Press.
引用
收藏
页码:412 / 420
页数:9
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