Preparation and electrical conductivity of three types of antimonic acid films
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Preparation and electrical conductivity of three types of antimonic acid films Kiyoshi Ozawa, Yoshio Sakka, and Muneyuki Amano National Research Institute for Metals, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305, Japan (Received 5 September 1997; accepted 5 January 1998)
Three types of antimonic acid (Sb2 O5 ? nH2 O) films, (111)-oriented and nonoriented polycrystalline films of cubic Sb2 O5 ? nH2 O and amorphous Sb2 O5 ? nH2 O films, were prepared on quartz glass substrates with a spin-coating technique using aqueous slurries, which were formed by reacting H2 O2 with metallic Sb powder or Sb(O-n-C3 H7 )3 . The morphologies and structures of the films were observed, and the electrical conductivity of the films was determined at 20 ±C in the relative humidity range 9–100%. The electrical conductivity of the (111)-oriented film, which increases from 1.69 3 1025 to 2.89 3 1023 S cm21 as the relative humidity changes from 11 to 85%, is approximately one order of magnitude larger than those of the nonoriented and amorphous films. I. INTRODUCTION
Antimonic acids (Sb2 O5 ? nH2 O) which can be classified as crystalline, cubic and monoclinic, and amorphous, are known to exhibit not only a high ion-exchange capacity,1 but also a high proton conductivity at room temperature.2–5 Since that proton conductivity is highly sensitive to humidity, these compounds are likely to be extremely useful in humidity-sensing materials. Sb2 O5 ? nH2 O powders have traditionally been synthesized by hydrolyzing SbCl5 4,5 or exchanging the Li1 ion in LiSbO3 with H1 ,1 and formed into bulk using conventional compression methods. However, to our knowledge, the preparation of Sb2 O5 ? nH2 O films, suitable for electrical conductivity measurements, has not yet been reported on except in our previous paper.6 However, Kudo et al.7–9 presented a unique technique for synthesizing new types of metal oxides with a high purity. A variety of metal oxides, powder or film, crystalline or amorphous, can easily be prepared from the peroxo-polyacid of metals, formed by reacting H2 O2 with metal powders or metal alkoxides. We also successfully prepared amorphous Sb2 O5 ? nH2 O films using a modification of this technique, and found that the amorphous film exhibits a high electrical conductivity: 1023 S cm21 at 100% relative humidity and 20 ±C.6 Furthermore, we found that (111)-oriented and nonoriented polycrystalline films of cubic Sb2 O5 ? nH2 O can be fabricated. The purpose of this work is to demonstrate, for the first time, how the (111)-oriented and nonoriented films were prepared, and their morphologies and structures. Next the electrical conductivities of these films are measured and compared with that of the amorphous film.
the procedures for synthesis of the (111)-oriented and nonoriented polycrystalline films of cubic Sb2 O5 ? nH2 O. The remarkable feature of these procedures is that (111)oriented films and nonoriented films can be successfully prepared using metallic Sb powder and antimony n-propoxide [Sb(O-n-
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