D4.3 - Thin-film calorimeter for high-temperature applications: Thermodynamic characterization on piezoelectric langasite temperature sensors
- AMA Conferences 2017
2017-05-30 - 2017-06-01
- Proceedings Sensor 2017
- D4 - Mechanical Sensors I
- A. Omelcenko, H. Wulfmeier, H. Fritze - Clausthal University of Technology, Goslar (Germany)
- 485 - 490
Thin-Film Calorimetry (TFC) is a measurement technique for in-situ analysis of thermal properties such as phase transformation temperatures and enthalpies of thin films and thin-film systems. It is applicable to metals, oxides and, for example, thin-film all-solid-state electrochemical cells. This technique takes advantage of the high temperature sensitivity of piezoelectric resonators. Here, high-temperature stable piezoelectric langasite single crystals are simultaneously operated as planar temperature sensors and substrates for the films of interest. Any generation or consumption of heat in the deposited films induces changes in the otherwise undisturbed resonance frequency. This work focuses on the thermal transport in these sensors to relate the frequency fluctuations with heat generation or consumption during phase transformations. Instead of using films with more or less unknown thermodynamic properties, well defined heat pulses are applied by resistive heating via platinum heating structures. Based on this approach, a detailed thermodynamic characterization of the TFC system is provided. The effects of short energy pulses and prolonged resistive heating is studied in vacuum and in pure Ar atmosphere. Different heat transfer processes and their timescales are identified and characterized quantitatively. The latter includes the influence of thermal convection on the heat dissipation.