Modified Lead Titanate
BM300 is a high performance, modified lead titanate piezoelectric ceramic. While it has good piezoelectric performance in the axial (thickness) direction, it has very low planar (radial) performance. In fact, for all practical purposes BM300 exhibits no transverse response. It intrinsically filters out planar signals and responds almost exclusively to axial inputs.
Consider a comparison: Soft PZT exhibits an axial to planar coupling coefficient ratio (k33 : k31) of approximately 2 : 1. For BM300 the planar coefficient is so small that ratio is 17 : 1.
(Read more about coupling coefficients on our Piezoelectric Fundamentals page.)
This anisotropy leads to another useful performance characteristic: high gh values. The hydrostatic piezoelectric voltage constant, gh, is a direct indicator of hydrophone sensitivity. It is related to the g coefficients for each axis by the following equation:
gh = g33 + g32 + g31
g33: axial (thickness) voltage constant
g32, g31: planar voltage constants
For piezoelectric ceramics g33 is positive, while g32 and g31 are negative, resulting in small (but usable) gh values. For lead titanate however, g33 is high while g32 and g31 are negligible, resulting in high gh values.
(Read more about g constants on our Piezoelectric Fundamentals page.)
The unique anisotropy of modified lead titanate is perhaps its most compelling feature. However, the material offers other useful performance characteristics. BM300 has a low dielectric constant and excellent stability over time.
Common applications for modified lead titanate:
Modified lead titanate has a negligible response to side loading and high gh & g33 values. As a result, it is an excellent piezoelectric material for receiving sensors that will be used under hydrostatic load, or any application in which the response to transverse modes needs to be minimized. Examples include:
- receive and send/receive sensors under hydrostatic load (e.g. downhole tools, hydrophones)
- lower frequency ultrasonic devices that may suffer from planar mode interference (e.g. NDT, NDE tools)
- single mode sensors (e.g. uni-axial accelerometers)