Sodium bismuth titanate or bismuth sodium titanium oxide (NBT or BNT) is a solid inorganic compound of

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

bismuth Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...

titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

and

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

of Na_0.5Bi_0.5TiO₃ or Bi_0.5Na_0.5TiO₃. This compound adopts the perovskite structure.

Synthesis

Na_0.5Bi_0.5TiO₃ is not a naturally occurring

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

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.

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 X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams due to interactions with the electrons around atoms. It occurs due to elastic scattering, when there is no change in the energy of the waves. ...

suggested Na_0.5Bi_0.5TiO₃ to adopt either a pseudo-cubic or a rhombohedral crystal structure. In 2010, based on the high-resolution single-crystal

data, a

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

structure (

space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...

Cc) was proposed. On heating, Na_0.5Bi_0.5TiO₃ transforms at 533 ± 5 K to a

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the Cube (geometry), cube becomes a rectangular Pri ...

structure (space group P4bm) and above 793 ± 5 K to cubic structure (space group Pmm).

Physical properties

Na_0.5Bi_0.5TiO₃ is a relaxor

ferroelectric In physics and materials science, ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoel ...

. Its optical band gap was reported to be in the 3.0–3.5 eV.

Applications

Various solid solutions with

perovskites including BaTiO₃, Bi_0.5K_0.5TiO₃ have been developed to obtain morphotropic phase boundaries to enhance the

piezoelectric Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied stress (mechanics), mechanical s ...

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 Lead zirconate titanate, also called lead zirconium titanate and commonly abbreviated as PZT, is an inorganic compound with the chemical formula . It is a ceramic perovskite material that shows a marked piezoelectric effect, meaning that the comp ...

for

actuator An actuator is a machine element, component of a machine that produces force, torque, or Displacement (geometry), displacement, when an electrical, Pneumatics, pneumatic or Hydraulic fluid, hydraulic input is supplied to it in a system (called an ...

applications.

Synthesis

Structure

Physical properties

Applications

References

Further reading