| GaPO4 | |
|---|---|
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| General | |
| Category | crystal |
| Chemical formula (or Composition) | GaPO4 |
| Identification | |
| Color | Clear |
| Crystal system | Trigonal |
| Crystal class | 32 or D3 (Schönflies) |
| Cleavage | None |
| Fracture | Conchoidal |
| Mohs Scale hardness | 5. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Use in chemistry In Chemistry, the empirical formula of a Chemical compound is a simple expression of the relative number of each type of Atom A crystal system is a category of Space groups which characterize Symmetry of structures in three dimensions with Translational symmetry in three directions In Crystallography, the hexagonal is one of the 7 Crystal system, it contains 7 Point groups. In Crystallography, a crystallographic point group is a set of Symmetry operations like rotations or reflections that leave a point fixed while moving each atom In Crystallography, a crystallographic point group is a set of Symmetry operations like rotations or reflections that leave a point fixed while moving each atom Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types A fracture is the (local separation of an object or material into two or more pieces under the action of stress. The Mohs scale of mineral hardness characterizes the scratch resistance of various Minerals through the ability of a harder material to scratch a softer material 5 |
| Refractive index | no=1. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium 605, ne=1. 623 |
| Pleochroism | None |
| Streak | White |
| Density | 3570 kg/m3 |
| Solubility | insoluble in pH = 5 - 8 |
| other properties | |
| Pyroelectricity | None |
| Particular characteristics | quartz isotype, piezoelectric effect up to 950°C (1742°F) |
Gallium phosphate (GaPO4 or gallium orthophosphate) is a colorless trigonal crystal with a hardness of 5. Pleochroism is an Optical phenomenon in which grains of a rock appear to be different colors when observed at different angles under a Petrographic microscope. The streak (also called powder color) of a Mineral is the Color of the powder produced when it is dragged across an unweathered surface The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. pH is the measure of the acidity or alkalinity of a Solution. Pyroelectric crystals are Crystals that generate electricity when heated Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Piezoelectricity is the ability of some materials (notably Crystals and certain Ceramics including bone to generate an Electric potential in response to Modifications GaPO4 possesses in contrast to quartz no α-β Phase transition, thus the low temperature structure (structure like α-quartz of GaPO4 5 on the Mohs scale. The Mohs scale of mineral hardness characterizes the scratch resistance of various Minerals through the ability of a harder material to scratch a softer material GaPO4 is isotypic with quartz, possessing very similar properties, but the silicon atoms are alternately substituted with gallium and phosphorus, thereby doubling the piezo electric effect. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Piezoelectricity is the ability of some materials (notably Crystals and certain Ceramics including bone to generate an Electric potential in response to GaPO4 has many advantages over quartz for technical applications, like a higher electromechanical coupling coefficient in resonators, due to this doubling. Electromechanical coupling coefficient is a numerical measure of the conversion efficiency between Electrical and acoustic energy in Piezoelectric A crystal oscillator is an Electronic circuit that uses the mechanical Resonance of a vibrating Crystal of piezoelectric material to create an Contrary to quartz, GaPO4 is not found in nature. Therefore, a hydrothermal process must be used to synthesize the crystal. Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat
Contents |
Modifications
GaPO4 possesses, in contrast to quartz, no α-β phase transition, thus the low temperature structure (structure like α-quartz) of GaPO4 is stable up to 970°C, as are most of its other physical properties. In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another Around 970°C another phase transition occurs which changes the low quartz structure into another structure similar with cristobalite. The mineral cristobalite is a high-temperature polymorph of Quartz and Tridymite.
Structure
The specific structure of GaPO4 shows the arrangement of tetrahedrons consisting of GaO4 and PO4 that are slightly tilted. Because of the helical arrangement of these tetrahedrons, two modifications of GaPO4 exist with different optical rotation (left and right). Optical rotation or optical activity is the rotation of linearly polarized Light as it travels through certain materials The term chiral (pronounced /ˈkaɪɹ(əl̩/ is used to describe an object that is non- superimposable on its mirror image
Sources
GaPO4 does not occur in nature; thus it must be grown synthetically. Presently, only one company in Austria produces these crystals commercially.
History and technical importance
Pressure sensors based on quartz have to be cooled with water for applications at higher temperatures (above 300°C). A piezoelectric sensor is a device that uses the Piezoelectric effect to measure Pressure, Acceleration, strain or Force Starting in 1994 it was possible to substitute these big sensors with miniaturized, non cooled ones, based on GaPO4. Further exceptional properties of GaPO4 for applications at high temperatures include its nearly temperature independent piezo effect and excellent electrical insulation up to 900°C. An insulator, also called a Dielectric, is a material that resists the flow of Electric current. For bulk resonator applications, this crystal exhibits temperature compensated cuts of up to 500°C while having Q factors comparable with quartz. A crystal oscillator is an Electronic circuit that uses the mechanical Resonance of a vibrating Crystal of piezoelectric material to create an A crystal oscillator is an Electronic circuit that uses the mechanical Resonance of a vibrating Crystal of piezoelectric material to create an Due to these material properties, GaPO4 is very suitable for piezoelectric pressure sensors at high temperatures and for high temperature microbalance. A piezoelectric sensor is a device that uses the Piezoelectric effect to measure Pressure, Acceleration, strain or Force A microbalance is an instrument capable of making precise measurements of weight of objects of relatively small mass of the order of a million parts of a Gram.
Literature
G. Gautschi: „Piezoelectric Sensorics“, published by Springer