Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films

Abstract

The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(MgNb)O-0.32PbTiO. Electric-field-driven enhancement of the pyroelectric response (as large as -550 μC m K) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert low-grade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm, 526 W cm and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.

Pyroelectric Energy Conversion in Doped Hafnium Oxide (HfO2) Thin Films on Area‐Enhanced Substrates

“…Thin‐film geometries can also enable fast thermal cycling, owing the fact that the volume of the active pyroelectric is small. As P = W · f , fast cycling also enables high power, as demonstrated with thin‐film devices fabricated with on‐chip heating elements, obtaining power densities of 3, 80, and 500 W cm −3 for barium titanate (BTO), PZT, and PMN‐PT films, respectively …”

“…The coupled response between electrical energy and thermal energy is a feature present in all ferroelectric materials arising primarily from the temperature dependence of the polarization state. These pyroelectric properties have been identified as the potential conversion mechanisms enabling waste‐heat scavenging, solid‐state cooling, and power‐beaming applications . Pyroelectric energy harvesting still largely relies on materials which are harmful to the environment, toxic, or not compatible with CMOS semiconductor manufacturing processes …”

Energy Applications of Magnetocaloric Materials

“…However, with the rapid development of caloric (ferroic) materials and technologies for refrigeration and air conditioning, caloric (ferroic) power generation is being revisited and prototype devices are being developed. Caloric power generation draws on specialized fields such as magnetocalorics (an aspect of thermomagnetics or pyromagnetics), electrocalorics (an aspect of pyroelectrics), and mechanocalorics (an aspect of thermoelastics) . Similar to refrigeration, multicaloric (multiferroic) power generation has also attracted research interest .…”

Piezoelectric Response of Polycrystalline Silicon‐Doped Hafnium Oxide Thin Films Determined by Rapid Temperature Cycles

“…This approach has been demonstrated before, utilizing heating via a pulsed laser 25. In addition, the extraction of pyroelectric coefficients by local Joule heating has been reported for various materials, including BaTiO 3, 26 PMN‐PT,27 and Si‐doped HfO 2 28,29. Here, a similar test structure is utilized, which is depicted in Figure A.…”