Yoshio Satoshi, Wakabayashi Masao, Adachi Kenji
Department of Computer-Aided Engineering, Sumitomo Metal Mining Co., Ltd. Ehime 792-0001 Japan
Ichikawa Research Center, Sumitomo Metal Mining Co., Ltd. Ichikawa Chiba 272-8588 Japan.
RSC Adv. 2020 Mar 11;10(18):10491-10501. doi: 10.1039/d0ra00505c.
Revisiting Wöhler's method (1824), Cs-doped tungsten bronzes were synthesized by reducing Cs-polytungstate at high temperature, and were pulverized into nanoparticles for determining their optical properties. The high-temperature reduced CsWO crystals absorbed strongly in the near-infrared, providing an improved luminous transparency with a less-bluish tint than normal CsWO synthesized in a reductive atmosphere. The high-temperature reduction caused an orthorhombic-to-hexagonal phase transformation and a nonmetal-metal transition, which was monitored by spectrophotometry, X-ray diffraction, and X-ray photoelectron spectroscopy measurements, assisted by a first-principles analysis using a DFT+U method. The high-temperature reduction of CsWO is concluded to decrease the number of W deficiencies and produce oxygen vacancies, releasing both free and trapped electrons into the conduction band and thereby activating the near-infrared absorption. The comparatively narrow bandgap of CsWO was identified as the origin of the less-bluish tint of the produced Cs tungsten bronzes.
重温维勒法（1824年），通过在高温下还原铯多钨酸盐合成了铯掺杂钨青铜，并将其粉碎成纳米颗粒以测定其光学性质。高温还原的CsWO晶体在近红外区域有强烈吸收，与在还原气氛中合成的普通CsWO相比，提供了更高的发光透明度且蓝光色调更淡。高温还原导致了正交晶系到六方晶系的相变以及非金属到金属的转变，通过分光光度法、X射线衍射和X射线光电子能谱测量对其进行监测，并借助使用DFT+U方法的第一性原理分析。得出结论，CsWO的高温还原减少了钨缺陷的数量并产生了氧空位，将自由电子和俘获电子释放到导带中，从而激活了近红外吸收。CsWO相对较窄的带隙被确定为所制备的铯钨青铜蓝光色调较淡的原因。
