Andraž Bradeško, our PhD student working on the project, presented the results on PMN-xPT ceramics and associated functional cantilevers on a conference in Atlanta, USA. The oral presentation and the poster contained the project results related to (i) the characterization of electromechanical, electrocaloric and thermal properties of (1–x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) in a wide range of compositions, relevant for the operation of the cooling device as the main idea of the project, and (ii) the effect of Joule heating arising during the electric-field cycling of PMN. Within the student competition, he received an award. The quality of the project’s research topic and its results have thus provided not only a recognition of our group in the research community, but have also given to the student an important reference to be used in his search of a postdoctoral position after completion of his PhD studies (which will take place this year).
E.02 International awards
COBISS.SI-ID: 30543143Andraž Bradeško, the PhD student working on the research project, presented for the first time the cooling system based on multifunctional cantilevers, which simultaneously exploit the electrocaloric and electromechanical effects. The presentation was given on one of the most important conferences (Thermag) in the field of emerging cooling technologies, held in Germany. The prototype was entirely conceptualized, fabricated and functionally validated within the project.
F.08 Development and manufacture of a prototype
COBISS.SI-ID: 31784999Joule heating, which typically causes an uncontrolled increase of the temperature of the material under applied electric field due to excessive electrical conductivity, is a key parameter that must be minimized to design and create efficient electrocaloric coolers. Despite this, the phenomenon is rarely investigated in the literature. Within an invited lecture, the principal project investigator, Dr. Tadej Rojac, presented the most recent project results related to the self-heating phenomena in Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-xPT) and Pb(Zr,Ti)O3 (PZT) ceramics occurring under electric field conditions that are expected in typical electrocaloric cooling devices. The aim of the talk was to disseminate, among the research community working on electrocalorics, the problems and consequences of the self-heating effects. We also explained the major causes of this detrimental phenomenon, which mostly arises due to the ferroelectric domain switching and the elevated electrical conductivity. In addition, we showed how the local electrical conductivity in PMN confined to grain boundaries, which was characterized by conductive atomic-force microscopy (c-AFM), critically increases during continuous electric-field cycling of the material. These results are particularly important for future cooling device based on the electrocaloric effect, considering that PMN is one of the most prominent candidates for such coolers. It is worth noting that this is the first invited presentation on a topic related to electrocalorics given to the principle project investigator, which confirms the quality and positive impacts of the research project.
B.04 Guest lecture
COBISS.SI-ID: 32062503In this invited talk, the collaborator of the project, Dr. Mojca Otoničar, presented the most recent project results related to the electromechanical (EM) behavior of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-xPT) ceramics in a wide compositional range. The talk was focused on the complex relationship between the macroscopic EM response of PMN-xPT and the local polar ordering, which was determined using atomic-scale microscopy. It is important to note that this lecture was the first invited that Dr. Otonicar received, confirming that the results of the project and the associated efforts of the involved participants critically contributed to the visibility of our research group, allowing us to obtain invited lectures.
B.04 Guest lecture
COBISS.SI-ID: 31465511In the scope of the project we developed and constructed two measurement systems for the characterization of the electrocaloric (EC) effect; one devoted for room-temperature measurements and the other for measurements in the temperature interval between -50 and 200°C. The room-temperature setup enables fast measurements of the EC effect on different samples. We also developed a dedicated software, which allows fatigue studies where samples are subjected to continuous cycling with electric field. The measurement system for characterization of EC temperature changes in the temperature range between -50 °C and 200 °C uses a differential scanning calorimeter for accurate temperature regulation and stabilization. Both setups were successfully used to characterize EC samples within the research project. In addition, we employed these setups in educational activities by organizing practical trainings on EC characterization of ceramic samples for undergraduate students of the Faculty of Natural Sciences and Engineering, University of Ljubljana.
F.17 Transfer of existing technologies, know-how, methods and procedures into practice
COBISS.SI-ID: 30301735