New phases in the ZrO{sub 2}-Bi{sub 2}O{sub 3} and HfO{sub 2}-Bi{sub 2}O{sub 3} systems
Journal Article
·
· Materials Research Bulletin
- Oregon State Univ., Corvallis, OR (United States)
New phases of the type M{sub 1{minus}x}Bi{sub x}O{sub 2{minus}x/2} with a defect fluorite structure have been prepared where M is Zr or Hf. These apparently metastable phases were prepared by precipitation from solution followed by calcination at 600 C. For the Hf{sub 1{minus}x}Bi{sub x}O{sub 2{minus}x/2} system, x ranges from x = 0.40 to x = 0.75. For the Zr{sub 1{minus}x}Bi{sub x}O{sub 2{minus}x/2} system, x ranges from x = 0.50 to x = 0.75. Heating the defect fluorite Hf{sub 1{minus}x}Bi{sub x}O{sub 2-x/2} phases to temperatures of 700 to 950 C leads to the formation of Bi{sub 2}Hf{sub 2}O{sub 7} with the Bi{sub 2}Sn{sub 2}O{sub 7} structure. Thus, Bi{sub 2}Hf{sub 2}O{sub 7} is pseudocubic, but apparently face centered tetragonal with a = 21.66 {angstrom} and c = 21.84 {angstrom}. When Bi{sub 2}Hf{sub 2}O{sub 7} is heated to 1000 C, it decomposes into HfO{sub 2} and Bi{sub 1.94}Hf{sub 0.06}O{sub 3.03} with the {beta}-Bi{sub 2}O{sub 3} structure. Heating the defect fluorite Zr{sub 1{minus}x}Bi{sub x}O{sub 2{minus}x/2} phases to higher temperatures never produced a Bi{sub 2}Zr{sub 2}O{sub 7} phase with the Bi{sub 2}Sn{sub 2}O{sub 7} structure. Instead, the compositional range of the defect fluorite structure steadily decreases with increasing temperature, and this phase had completely decomposed at 750 C into ZrO{sub 2} and Bi{sub 1.84}Zr{sub 0.16}O{sub 3.08} with the {beta}-Bi{sub 2}O{sub 3} structure.
- OSTI ID:
- 638352
- Journal Information:
- Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 7 Vol. 33; ISSN MRBUAC; ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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