In situ high-pressure synchrotron X-ray powder diffraction study of tunnel manganese oxide minerals: hollandite, romanechite, and todorokite

Gil Chan Hwang, Jeffrey E. Post, Yongjae Lee

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

In situ high-pressure synchrotron X-ray powder diffraction study of three tunnel manganese oxide minerals (hollandite with 2 × 2 MnO6octahedra tunnels, romanechite with 2 × 3 tunnels, and todorokite with 3 × 3 tunnels) was performed using a diamond anvil cell and nominally penetrating alcohol and water mixture as a pressure-transmitting medium up to ~8 GPa. Bulk moduli (B0)calculated using Murnaghan’s equation of state are inversely proportional to the size of the tunnel, i.e., 134(4) GPa for hollandite (I2/m), 108(2) GPa for romanechite (C2/m), and 67(5) GPa for todorokite (P2/m). On the other hand, axial compressibilities show different elastic anisotropies depending on the size of the tunnel, i.e., $$ \beta_{0}^{a} $$β0a(a/a0)=−0.00066(3) GPa−1, $$ \beta_{0}^{b} $$β0b (b/b0)=0.00179(8) GPa−1,$$ \beta_{0}^{c} $$β0c(c/c0)=0.00637(4) GPa−1[c > b > a]for hollandite;$$\beta_{0}^{a} $$β0a(a/a0)=0.00485(4) GPa−1,$$ \beta_{0}^{b} $$β0b (b/b0)=0.0016(1) GPa−1, $$ \beta_{0}^{c} $$β0c(c/c0)=0.00199(8) GPa−1[a > c > b] for romanechite; and $$ \beta_{0}^{a} $$β0a(a/a0)=0.00826(9)GPa−1,$$ \beta_{0}^{b} $$β0b(b/b0)=0.0054(1)GPa−1, $$ \beta_{0}^{c}$$β0c(c/c0)=0.00081(8) GPa−1[a > b > c] for todorokite.Overall, the degree of tunnel distortion increases with increasing pressure and correlates with the size of the tunnel, which is evidenced by the gradual increases in the monoclinic β angles up to 3 GPa of 0.62°,0.8°, and 1.15° in hollandite, romanechite, and todorokite, respectively. The compression of tunnel manganese oxides is related to the tunnel distortion and the size of the tunnel.

Original languageEnglish
Pages (from-to)405-411
Number of pages7
JournalPhysics and Chemistry of Minerals
Volume42
Issue number5
DOIs
Publication statusPublished - 2015 May 1

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Geochemistry and Petrology

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