Sodium bismuth titanate

Na_0.5Bi_0.5TiO₃ is not a naturally occurring mineral and several synthesis routes to obtain the compound have been developed. It can be easily prepared by solid state reaction between Na₂CO₃, Bi₂O₃ and TiO₂ at temperatures around 850 °C.

{{main|Perovskite (structure)}}

The exact room-temperature crystal structure of sodium bismuth titanate has been a matter of debate for several years. Early studies in the 1960s using X-ray diffraction suggested Na_0.5Bi_0.5TiO₃ to adopt either a pseudo-cubic or a rhombohedral crystal structure.{{cite journal|author1=Smolenskii, G. |author2=Isupov, V. |author3=Agranovskaya, A. |author4=Krainik, N. | title =New ferroelectrics of complex composition. | journal =Sov. Phys. Solid State |year =1961| volume = 2 | pages =2651–2654}} In 2010, based on the high-resolution single-crystal X-ray diffraction data, a monoclinic structure (space group Cc) was proposed. On heating, Na_0.5Bi_0.5TiO₃ transforms at 533 ± 5 K to a tetragonal structure (space group P4bm) and above 793 ± 5 K to cubic structure (space group Pm{{overline|3}}m).{{cite journal|author1=Zvirgzds, J.A. |author2=Kapostin, P.P. |author3=Zvirgzde, J.V. |author4=Kruzina, T.V. | title =X-ray study of phase transitions in ferroelectric Na_0.5Bi_0.5TiO₃| journal =Ferroelectrics |year =1982 | volume =40|issue=1 | pages = 75–77|doi=10.1080/00150198208210600 |bibcode=1982Fer....40...75Z }}

Na_0.5Bi_0.5TiO₃ is a relaxor ferroelectric. Its optical band gap was reported to be in the 3.0–3.5 eV.{{cite journal|author1=Bousquet, M. |author2=Duclere, J.R. |author3=Orhan, E. |author4=Boulle, A. |author5=Bachelet, C. |author6=Champeaux, C | title = Optical properties of an epitaxial Na_0.5Bi_0.5TiO₃ thin film grown by laser ablation: Experimental approach and density functional theory calculations| volume = 107| pages = 104107–104107–13| journal = J. Appl. Phys.|year = 2010|issue=10 |doi=10.1063/1.3400095|bibcode=2010JAP...107j4107B }}

{{main|Piezoelectricity}}

Various solid solutions with tetragonal ferroelectric perovskites including BaTiO₃,{{cite journal|author1=Takenaka, T. |author2=Maruyama, K.-I. |author3=Sakata, K. | title = (Bi_1/2Na_1/2)TiO₃-BaTiO₃ system for lead-free piezoelectric ceramics.| volume = 30| pages = 2236–2239| journal = Jpn. J. Appl. Phys. Part 1|year = 1991|issue=9S |doi=10.1143/JJAP.30.2236|bibcode=1991JaJAP..30.2236T |s2cid=124093028 }} Bi_0.5K_0.5TiO₃Sasaki, A.; Chiba, T.; Mamiya, Y.; Otsuki, E. Dielectric and piezoelectric properties of (Bi_0.5Na_0.5)TiO₃-(Bi_0.5K_0.5)TiO₃ systems. Jpn. J. Appl. Phys. Part 1 1999, 38, 5564–5567. have been developed to obtain morphotropic phase boundaries to enhance the piezoelectric properties of Na_0.5Bi_0.5TiO₃. The extraordinarily large strain generated by a field-induced phase transition in sodium bismuth titanate-based solid solutions prompted researchers to investigate its potential as an alternative to lead zirconate titanate for actuator applications.{{cite journal|author1=Reichmann, K. |author2=Feteira, A., Li M. | title = Bismuth Sodium Titanate Based Materials for Piezoelectric Actuators| volume = 8| pages = 8467–8495| journal = Materials|year = 2015|issue=12 |doi=10.3390/ma8125469|pmid=28793724 |pmc = 5458809|bibcode=2015Mate....8.8467R |doi-access=free }}

{{reflist|30em}}

• Lead-Free Piezoelectrics, Ed. Shashank Priya and Sahn Nahm,(2012), Springer-Verlag, New York. {{doi|10.1007/978-1-4419-9598-8}}.

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Category:Titanates

Category:Bismuth compounds

Category:Ceramic materials

Category:Piezoelectric materials

Category:Ferroelectric materials

Category:Perovskites

Category:Sodium compounds