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6.11J: Structure - Perovskite (\(CaTiO_3\))

  • Page ID
    2588
  • Figure 2: A distroted perovskite SmNiO3 with orthorhombic symmetry.
    Figure 2: Superconducting Sr2RuO4 (http://wikis.lib.ncsu.edu/index.php/Perovskite)

    Some other unique properties that sets perovskites apart and makes them ideal for technological applications include: it is the only crystal structure that is ferroelectric (spontaneous alignment of the electric dipoles caused by interactions between them) not because of an external magnetic field but due to its crystal structure, its ferro-, pyro-, and piezo-electric properties, and structural properties such as durability and chemical flexibility.

    References

    1. Catherine E. Housecroft and Alan G. Sharpe. Inorganic Chemistry (3rd Edition). Pearson Education Limited, 2008
    2. Wolfram, Thomas. Electonic and optical properties of D-band perskovites. Caimbridge, New York: Caimbridge University Press, 2006
    3. http://wikis.lib.ncsu.edu/index.php/Perovskite
    4. Hongyan Yanga, Yuji Ohishia, Ken Kurosakia, Hiroaki Muta, Shinsuke Yamanaka (2010). Thermomechanical properties of calcium series perovskite-type oxides. Journal of Alloys and Compounds 504 (2010) 201–204
    5. Data Sheet for Perovskite (CaTiO3). Mineral Data Publishing, version 1 (2005)
    6. A. Boudali, A. Abada, M. Driss Khodja, B. Amrani, K. Amara, F. Driss Khodja and A. Elias (2010). Calculation of structural, elastic, electronic, and thermal properties of orthorhombic CaTiO3. Physica B: Condensed Matter, Volume 405 Issue 18 15 September 2010, Pages 3879-388
    7. Motohiko Murakame, Kei Hirose, Katsuyuki Kawamura, Nagayoshi Sata, Yasuo Ohishi.(2004) Post Perovskite Phase Transition in MgSiO3. Science Magazine, Vol. 304 No. 5672 Pgs. 855-858.
    8. Professor Kim, Professor in the CHMS department at UC Davis

    Important Questions

    Q: What are some properties that make the perovskite structure unique?

    A: Ferro- and Piezo-electric properties, and high oxygen ion vacancy tolerance.

    Q: List 2-3 modern applications of the perovskite structure.

    A: SOFCs, RAM devices and HTSCs.

    Q: Why are perovskite type materials especially useful in SOFCs (solid oxide fuel cells)?

    A: High tolerance for oxygen ion deficiencies raises conductivity.

    Q: What is the difference between cubic and orthorhombic perovskite?

    A: The dimensions of the orthorhombic unit cell are unequal.

    Q: Given that perovskites in an orthorhombic configuration have lattice constants of roughly a=5.4338, b=5.4886, and c=7.6841 angstroms(A), and using the figures above, determine the density. Each calcium ion is located at the center of the octahedra and has 12-fold coordination with the oxygen, and the titanium ions are located at the corners and has six-fold coordination with oxygen.

    A: The orthorhombic configuration, which is the most common configuration in perovskite materials, has lattice constants of a=5.4338, b=5.4886, and c=7.6841 angstroms. One orthorhombic unit cell contains four A's, which are the calciums for example, four B's and 12 O's. For the case of CaTiO3, using the lattice constants and the number of atoms per cell listed previously, the density of orthorhombic CaTiO3 is 3.944 g/cm3. A sample calculation is provided below.

    Volume(cell) = 5.4338*5.4886*7.6841 = 229.17 A3 = 2.292*10-22 cm3

    Mass(cell) = 4*MW(Ca)+4*MW(Ti)+12*MW(O) = 542.92 g/mol = 9.0322*10-22 g/#

    Mass/Volume=Density=3.944 g/cm3

    Contributors

    • Matthew Ibbotson: Undergraduate in Chemical Engineering, Senior