In recent years the electrocaloric effect has gained the substantial interest of researchers
due to its potential applications in commercial cooling. The high theoretical effciency of
electro-thermal conversion places this phenomenon as a potential alternative to commercial
vapour-compression refrigerators. Success in such solid state cooling is anticipated to lead
to global scale energy savings and reduction in the emission of greenhouse gases.
Most of the focus has been directed towards the achievement of high values of the
electrocaloric effect temperature change ∆T EC . High values of around 10 K and more have
been reported. However little attention has been given to the methods of measurements
and their uncertainties.
This work aims to use a metrological approach to study the electrocaloric phenomenon,
to compare certain methods and to explore these measurements and their uncertainties.
There are various ways to quantify the electrocaloric effect and various parameters infuence
the direct measurements of ∆T EC . Here a direct method using infrared imaging is
employed for the spatial and time-resolved temperature measurements of electrocaloric
bodies. A set of the parameters infuencing the∆T EC is determined. Based on these
quantifed contributions, an uncertainty for such measurements is reported. The calibration
of the imager is performed to validate the traceability of measurements, and a further set
of characterisation apparatus was implemented to establish its performance.
A bulk Ba 0.65 Sr 0.35 TiO 3 sample was employed as a cross reference specimen in an inter-laboratory
comparison involving infrared imaging and two types of differential scanning calorimetry.
Within the scope of this work, two commercial ceramic material compositions were characterised;
a multilayer capacitor and a PMN-PT ceramic. First, BaTiO 3 in form of a multilayer
ceramic capacitor was used to establish the optimal performance of such a structure
and to investigate the in-situ measurements. In this measurement there were substantial
differences in ∆T EC depending on where on the sample (surface vs. interior) the measurement
was made and an explanation for this difference is suggested. Second, the polycrystalline
Pb(Mg 1/3 Nb 2/3 )−PbTiO 3 ceramic sample was used investigate other sources of uncertainties
arising from the mechanical coupling during electrocaloric measurements, estimated to
account for up to 20% of the observed electrocaloric effect.