It depends upon the application you require from that material: For example if you require for actuator application then d33 is most important parameter. However if you require for sensor application then g33 is important parameter rather than d33. Another important parameter which you always want to increase in electromechanical coupling factor.

Generally, what differs PMN-PT family from the rest is its electromechanical coupling coefficient k. The higher k, the higher sensitivity and bandwidth. The biggest limitation of this material is property stability, first due to low transition temperature (Rhombohedral to Tetragonal) of below 150 dC, secondly due to property variation caused by materials processing parameters (segregation coefficient amongst others). Recent effort to address these issues by dopant (such as In) to increase transition temperature (hence application temperature) and enhancing processing methods. For more details please view www.innoviamaterials.com.

How do you test polarization ?