In the context of piezoelectric transducers, "g" and "d" are typically used to represent different material properties of the piezoelectric material and its geometry.
These properties are important for understanding the behavior and performance of the transducer."g" (sometimes represented as "g11" or "g31"): This parameter represents the piezoelectric voltage constant or the piezoelectric charge constant, depending on the specific application. It is a material property and is typically measured in units of C/N (coulombs per newton) or Vm/N (volts per meter per newton). The value of "g" is related to the ability of the piezoelectric material to generate an electrical charge (or voltage) when subjected to mechanical stress. A larger value of "g" indicates a more efficient conversion between mechanical and electrical energy.
"d" (sometimes represented as "d31" or "d33"): This parameter represents the piezoelectric charge coefficient, and it is also a material property. It is typically measured in units of pC/N (picoCoulombs per newton) or pm/V (picometers per volt). "d" describes the ability of the piezoelectric material to generate a mechanical deformation (strain) when subjected to an electrical field. In other words, it quantifies the piezoelectric effect in the material, where applying an electrical voltage results in mechanical displacement or strain.
The relationship between "g" and "d" can be expressed mathematically through the following equation:
g = d * ε
Where:
"g" is the piezoelectric voltage constant or charge constant.
"d" is the piezoelectric charge coefficient.
ε (epsilon) is the permittivity of the material.
This equation shows that "g" and "d" are related through the material's permittivity. The exact relationship can vary depending on the specific material and its crystal structure. However, in practical terms, understanding both "g" and "d" is crucial for designing and using piezoelectric transducers effectively, as they determine how the transducer converts between mechanical and electrical energy.
Piezoelectric materials can have multiple "d" and "g" coefficients due to their anisotropic nature, meaning their properties may vary with crystal orientation. The specific coefficient used in a particular application depends on the orientation and desired functionality of the transducer.