Potassium niobate (KNbO
3) is an
inorganic compound with the formula KNbO
3. A colorless solid, it is classified as a
perovskite
Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as (XIIA2+VIB4+X2−3), known a ...
ferroelectric
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 piezoelectric and pyroelectric, with the ad ...
material.
It exhibits nonlinear optical properties, and is a component of some lasers.
Nanowires of potassium niobate have been used to produce tunable coherent light.
Structure
On cooling from high temperature, KNbO
3 undergoes a series of structural
phase transition
In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states o ...
s. At 435 °C, the crystal symmetry changes from cubic centrosymmetric (Pmm) to
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 becomes a rectangular prism with a squar ...
non-centrosymmetric (P4mm). On further cooling, at 225 °C the crystal symmetry changes from tetragonal (P4mm) to
orthorhombic (Amm2) and at −50 °C from
orthorhombic (Amm2) to
rhombohedral
In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be us ...
(R3m).
Applications and research
In addition to research in electronic memory storage,
potassium niobate is used in
resonant doubling.
This technique allows small infrared lasers to convert output into blue light, a critical technology for the production of blue lasers and technology dependent upon them.
Potassium niobate has been found useful in many different areas of
materials science,
including properties of
lasers
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
,
,
and it has been used to study the optical properties of particulate
composite materials
A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...
.
Safety
The for potassium niobate is 3000 mg/kg (oral, rat).
References
{{Niobium compounds
Potassium compounds
Niobates
Nonlinear optical materials
Ferroelectric materials
Perovskites
Piezoelectric materials