Barium phosphate, also known as barium orthophosphate, is an inorganic
phosphate
Phosphates are the naturally occurring form of the element phosphorus.
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...
of
barium
Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.
Th ...
with the molecular formula Ba
3(PO
4)
2. It is usually found as a white, odorless powder which is insoluble in water.
Synthesis
The general chemical reaction for the synthesis of barium phosphate powder, using the
sol-gel process, is:
3 Ba(NO
3)
2 + 2 NH
4H
2PO
4 → Ba
3(PO
4)
2 + 2 NH
4NO
3 + 4 HNO
3
Barium phosphate is formed as a
precipitate
In an aqueous solution, precipitation is the "sedimentation of a solid material (a precipitate) from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemic ...
.
Structure
Its
crystal structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...
is
rhombohedral
In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a special case of a parallelepiped in which all six faces are congruent rhombus, rhombi. It can be used to define the rhombohedral lattice system, a Ho ...
with a
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 ...
of ''R'm'', identical to that of
strontium phosphate.
Properties
Barium phosphate exhibits properties such as high
refractive index
In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
, low melting point, low
glass transition temperature
The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rub ...
, high transparency to
ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
light, and high
thermal expansion coefficient
Thermal expansion is the tendency of matter to increase in length, area, or volume, changing its size and density, in response to an increase in temperature (usually excluding phase transitions).
Substances usually contract with decreasing temp ...
.
Applications
Barium phosphate finds uses in industrial applications, including optical applications like preparation of
glasses
Glasses, also known as eyeglasses (American English), spectacles (Commonwealth English), or colloquially as specs, are vision eyewear with clear or tinted lenses mounted in a frame that holds them in front of a person's eyes, typically u ...
with special properties for pulsed
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'' originated as an acronym for light amplification by stimulated emission of radi ...
, and preparation of
solders for glass to glass bonding. It can also be used in development of hydrogen / fuel sensors.
See also
*
Barium metaphosphate
References
{{Phosphates
Inorganic compounds
Phosphates
Barium compounds