TY - THES

T1 - Electrical cycling and failure analysis of a lead-free piezoceramic

AU - Neumüller, Johannes

N1 - embargoed until 10-09-2029

PY - 2024

Y1 - 2024

N2 - Piezoceramics are materials with outstanding piezoelectric properties which, due to their ceramic origin, can also be manufactured as multilayer components using established ceramic manufacturing processes. This allows the economical use of piezo components for sensor technology, such as ultrasonic sensors, and actuators, such as injection nozzles in automotive applications. Lead-containing ceramics - mainly lead zirconate titanate (PZT) - are particularly suitable for piezoelectric applications due to their properties, but they represent a risk to health and the environment according to an EU directive (RoHS Regulation). Therefore, they can only be used to a limited extent in the electronics sector. Potassium sodium niobate (KNN) could be a possible replacement, if the challenges of optimising the piezoelectric properties and of the manufacturing process, which, for example, includes metal-ceramic co-sintering, could be overcome. For industrial use, durability and cyclic stability are also required, which is why this thesis deals with developing a setup for their characterisation. As a result, a setup for cyclic loading and monitoring of the material condition was created and designed for testing durations of several weeks. Piezoceramic materials are characterised by a high insulation resistance. Degradation of the material can lead to reduced electrical resistance and failure due to localised electrical breakdowns within the component, which is why this property was chosen to determine the material condition. Infrared thermography was used to analyse degraded components. Using the lock-in method, it was possible to localise breakthrough paths that exhibit a power conversion in the milliwatt range and, thus, temperature variations in the range of a few millikelvins. This was demonstrated using a sample that showed localised degradation during the load test. Further investigation revealed a slight non-linearity of the resistance behaviour in the investigated voltage range.

AB - Piezoceramics are materials with outstanding piezoelectric properties which, due to their ceramic origin, can also be manufactured as multilayer components using established ceramic manufacturing processes. This allows the economical use of piezo components for sensor technology, such as ultrasonic sensors, and actuators, such as injection nozzles in automotive applications. Lead-containing ceramics - mainly lead zirconate titanate (PZT) - are particularly suitable for piezoelectric applications due to their properties, but they represent a risk to health and the environment according to an EU directive (RoHS Regulation). Therefore, they can only be used to a limited extent in the electronics sector. Potassium sodium niobate (KNN) could be a possible replacement, if the challenges of optimising the piezoelectric properties and of the manufacturing process, which, for example, includes metal-ceramic co-sintering, could be overcome. For industrial use, durability and cyclic stability are also required, which is why this thesis deals with developing a setup for their characterisation. As a result, a setup for cyclic loading and monitoring of the material condition was created and designed for testing durations of several weeks. Piezoceramic materials are characterised by a high insulation resistance. Degradation of the material can lead to reduced electrical resistance and failure due to localised electrical breakdowns within the component, which is why this property was chosen to determine the material condition. Infrared thermography was used to analyse degraded components. Using the lock-in method, it was possible to localise breakthrough paths that exhibit a power conversion in the milliwatt range and, thus, temperature variations in the range of a few millikelvins. This was demonstrated using a sample that showed localised degradation during the load test. Further investigation revealed a slight non-linearity of the resistance behaviour in the investigated voltage range.

KW - thermography

KW - lead-free piezoceramic

KW - electrical cycling

KW - degradation

KW - KNN

KW - Thermographie

KW - bleifreie Piezokeramik

KW - elektrische Zyklenbelastung

KW - Degradierung

KW - KNN

M3 - Master's Thesis

ER -