Influence of the polarization anisotropy on the electrocaloric effect in epitaxial PMN-PT thin films

Abstract

Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) compounds, which are typically used for high performance actuator applications due to their outstanding piezoelectric properties, show, in addition, a pronounced electrocaloric (EC) effect. The study of epitaxial films is a useful tool to analyze the correlation between the microstructure and EC properties in order to optimize the performance of these materials. Therefore, the 0.9PMN-0.1PT films were grown by a pulsed laser deposition on (001) as well as (111) oriented SrTiO3 single crystalline substrates using a La0.7Sr0.3CoO3 buffer as the bottom electrode and additional Au top electrodes. The structural properties determined by a high resolution X-ray and electron microscopy techniques indicated an undisturbed epitaxial growth. The anisotropy of the ferroelectric domain structure was investigated by a vertical and lateral piezoresponse force microscopy showing clear differences between the two orientations. A significant reduction of the thermal hysteresis was observed in the T-dependent polarization measurements for (111) oriented PMN-PT films, whereas the indirectly determined EC properties yield a maximum ΔT of around 15 K at 40 °C for a field of about 400 kV/cm for both film orientations

Highly reversible extrinsic electrocaloric effects over a wide temperature range in epitaxially strained SrTiO3 films

“…Epitaxial oxide films present large areas of high-quality crystalline material in a single orientation, but are rarely used to study EC effects [37][38][39] even though EC effects are not well understood. Our demonstration that epitaxial strain yields highly reversible extrinsic EC effects over a wide temperature range immediately implies that extrinsic EC effects should be investigated in many systems, via Landau theory and experimentally.…”

“…The experimental study of EC effects in epitaxial films is rare [37][38][39] , as is the study 40,41 of EC effects associated with second-order transitions, where the electric field suppresses polarization fluctuations 42 , unlike first-order transitions, where the driven transition yields latent heat. Our strain-induced transition expands the limited set of existing EC materials and should inspire further studies in various geometries.…”

Tuning the Semiconducting Properties in Co3O4/PMN–PT Heterostructures by Oxygen Vacancies and Domain Structure

“…20 The ferroelectric domain distribution and surface morphology of the PMN−PT substrates, related to the substrate orientation, can affect the electrical properties of the deposited film. 21 Kinks existing at the domain walls of PMN−PT are also observed in the surface morphology in graphene/PMN−PT heterostructures, which could enhance the charge trapping effects at the interface between the graphene and ferroelectric materials. 22 Moreover, the different orientations of the PMN−PT substrates can bring diverse ferroelectric and piezoelectric characteristics, which can affect the modulation of the PMN−PT substrates.…”

“…The unique surface morphology and superior ferroelectricity of 0.7Pb­(Mg 1/3 Nb 2/3 )­O 3 –0.3PbTiO 3 (PMN–PT) substrates can efficiently modulate the electrical properties of semiconductors by changing the external electric field . The ferroelectric domain distribution and surface morphology of the PMN–PT substrates, related to the substrate orientation, can affect the electrical properties of the deposited film . Kinks existing at the domain walls of PMN–PT are also observed in the surface morphology in graphene/PMN–PT heterostructures, which could enhance the charge trapping effects at the interface between the graphene and ferroelectric materials .…”

Growth mode and strain effect on relaxor ferroelectric domains in epitaxial 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3/SrRuO3 heterostructures

“…The exact origin of the giant piezoelectric response in PMN-PT is still under debate due to the high complexity of the microstructure and the local polar order/disorder at the MPB. [10][11][12][13][14][15] Despite the great attention received by PMN-PT in thin lm form, in particular for energy harvesting, energy storage and cooling applications, [16][17][18][19][20][21] there is still a lack of knowledge regarding epitaxial thin lms, particularly concerning correlations between the local atomic structure/strain and physical properties. 10,[22][23][24][25][26][27] Thus, understanding of the domains in relaxor ferroelectric thin lms and their evolution under external parameters such as epitaxial strain is crucial for practical applications.…”