Barium orthotitanate explained

Barium orthotitanate is the inorganic compound with the chemical formula Ba₂TiO₄. It is a colourless solid that is of interest because of its relationship to barium titanate, a useful electroceramic.

Structure

The solid has two known phases: a low-temperature (β) phase with P2₁/n symmetry^[1] and a high-temperature (α) phase with P2₁nb symmetry.^[2] The structure of Ba₂TiO₄ is unusual among the titanates because its titanium atoms sit in a four-oxygen tetrahedron rather than a six-oxygen octahedron.^[3]

Production

It forms as white crystals from a melt of BaCl₂, BaCO₃ and TiO₂^[4] or from just sintering BaCO₃ and TiO₂.^[5] Another method of preparation is heating pellets of Ba(OH)₂ and TiO₂.^[6] Additionally, there are polymer precursor, sol-gel and reverse micellar routes to Ba₂TiO₄ synthesis. Ba₂TiO₄ has also been successfully grown as a thin film with chemical vapor deposition.^[7]

Properties

• Room temperature entropy – 47.0 cal/deg. mol
• Dielectric constant – 20 (at 100 kHz)^[8]
• It is hygroscopic and decomposes with swelling in moist air.^[9]

Barium orthotitanate can remove up to 99.9% of from a high-temperature gas stream^[10] by the reaction:

+ → +

References

1. Wu. Kang Kun. Brown. I. D.. The Crystal Structure of β-Barium Orthotitanate, β-Ba₂TiO₄, and the Bond Strength-Bond Length Curve of Ti-O. Acta Crystallographica. 10 April 1973. B29. 9. 2009–2012. 10.1107/S0567740873005959.
2. Günter. John R.. Jameson. Geoffrey B.. Orthorhombic Barium Orthotitanate, α-Ba₂TiO₄. Acta Crystallographica. 14 September 1983. C40. 207–210. 10.1107/S0108270184003619.
3. Shanker. Vishnu. Ahmad. Tokeer. Ganguli. Ashok K.. Investigation of Ba_2–xSr_xTiO₄: Structural aspects and dielectric properties. Bulletin of Materials Science. 27. 5. October 2004. 421–427. 10.1007/BF02708558. free.
4. Bland. J. A.. The Crystal Structure of Barium Orthotitanate, Ba₂TiO₄. Acta Crystallographica. August 1961. 14. 8. 875–881. 10.1107/S0365110X61002527. 1961AcCry..14..875B .
5. Bobovich. Ya. S.. The Raman Scattering of Barium Orthotitanate. Optics and Spectroscopy. 13. 254–255.
6. Todd. S. S.. Lorenson, R.E.. Heat Capacities at Low Temperatures and Entropies at 298.16K. of Orthotitanates of Barium and Strontium. Journal of the American Chemical Society. August 1952. 74. 15. 2043–2045. 10.1021/ja01135a014.
7. Guo. Dongyun. Goto, Takashi. Wang, Chuanbin. Shen, Qiang . Zhang, Lianmeng . amp . High-speed growth of (103)-oriented Ba₂TiO₄ film by laser chemical vapor deposition. Materials Letters. 70. 2012. 135–137. 10.1016/j.matlet.2011.11.094.
8. Ahmad. Tokeer. Ganguli, Ashok K.. Synthesis of nanometer-sized particles of barium orthotitanate prepared through a modified reverse micellar route: Structural characterization, phase stability and dielectric properties. Journal of Materials Research. 1 October 2004. 19. 10. 2905–2912. 10.1557/JMR.2004.0406. 2004JMatR..19.2905A.
9. Book: Piezoelectric Ceramics. 1971. Academic Press. London and New York. 0123795508. Jaffe, Bernard. Cook Jr., William R.. Jaffe, Hans. 62. 5. Barium Titanate.
10. Saito. Yoshinori. Hideto. Sato. Yukio. Sakabe. CO₂ Recovery at High Temperatures Using Ba₂TiO₄. Journal of Chemical Engineering of Japan. 20 May 2008. 41. 5. 441–446. 10.1252/jcej.07WE236.