Title
Functionally graded ferroelectric polyetherimide composites for high temperature sensing
Author
Khanbareh, H.
Hegde, M.
Bijleveld, J.C.
van der Zwaag, S.
Groen, P.
Publication year
2017
Abstract
High temperature ferroelectrics for thermally stable devices that can detect pressure and temperature are of great industrial interest. Here we describe composites of lead titanate (PT) particle-polyetherimide (PEI) polymers with stable dielectric and piezoelectric properties over a broad range of temperature and frequency. The reported materials have a low dielectric loss (tanδ ∼ 0.001 at 1 kHz) and a high piezoelectric voltage coefficient of 100 mV m N-1 at record temperatures of 175 °C. We demonstrate that a small ceramic loading leads to a significant change in thermally stable piezoelectric behavior, while the processability as well as mechanical properties remain comparable to those of the neat polymer. Careful design of the microstructure is performed by dielectrophoretic assembly of ferroelectric PT micro-particles to induce micro-wire configurations, which is shown to be a key element in attaining high functionality at low ceramic loading. Thermal imidization of the composites is performed in two steps, first partial imidization at 60 °C to form free standing films containing polyamic acid, followed by full imidization at 200 °C and 300 °C. The presence of highly polar polyamic acid results in higher dielectric permittivity and electrical conductivity that facilitate efficient poling. Upon complete imidization of the films at 300 °C the dielectric and piezoelectric properties are tested at elevated temperatures. A fully imidized composite contains completely closed imide groups, resulting in a thermally stable material with a very low dielectric loss that maintains more than 85% of its room temperature piezoelectric sensitivity up to 175 °C. The room temperature piezoelectric voltage coefficient shows more than 400% improvement over that of PT ceramics.
Subject
Ceramic materials
Dielectric devices
Dielectric losses
Ferroelectric materials
Polymers
Thermodynamic stability
Dielectric properties
Piezoelectric properties
High-temperature sensing
Piezoelectric voltage
Pressure
Temperature
Dielectric materials
Industrial Innovation
Nano Technology
HOL - Holst
TS - Technical Sciences
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DOI
https://doi.org/10.1039/c7tc02649h
TNO identifier
781336
ISSN
2050-7534
Source
Journal of Materials Chemistry C, 5 (5), 9389-9397
Document type
article