Editing Pyroelectricity (section)

== Applications ==
Pyroelectric materials, which generate electrical charges in response to temperature fluctuations, have diverse applications due to their ability to convert thermal energy into electricity or detect thermal changes. Key applications include:

=== Heat sensors ===
Very small changes in temperature can produce a pyroelectric potential. [[Passive infrared sensor]]s are often designed around pyroelectric materials, as the heat of a human or animal from several feet away is enough to generate a voltage.<ref>{{Cite journal |title=Target Classification Using Pyroelectric Infrared Sensors in Unattended Wild Ground Environment |journal=International Journal on Smart Sensing and Intelligent Systems |volume=6 |issue=5}}</ref>

* '''Thermal Sensors''': Infrared detectors, fire alarms, gas sensors, and motion sensors utilize high voltage/current responsivity. Lead-based materials (e.g., PMN-PT) excel here due to superior figures of merit (FoMs).<ref>{{Cite journal |last1=Ranu |last2=B |first2=Uthra |last3=Sinha |first3=Rahul |last4=Agarwal |first4=Pankaj B. |date=2022-03-15 |title=CMOS compatible pyroelectric materials for infrared detectors |url=https://linkinghub.elsevier.com/retrieve/pii/S1369800121007083 |journal=Materials Science in Semiconductor Processing |volume=140 |pages=106375 |doi=10.1016/j.mssp.2021.106375 |issn=1369-8001}}</ref><ref name=":0">{{Cite journal |last1=Thakre |first1=Atul |last2=Kumar |first2=Ajeet |last3=Song |first3=Hyun-Cheol |last4=Jeong |first4=Dae-Yong |last5=Ryu |first5=Jungho |date=2019-05-10 |title=Pyroelectric Energy Conversion and Its Applications—Flexible Energy Harvesters and Sensors |journal=Sensors |language=en |volume=19 |issue=9 |pages=2170 |doi=10.3390/s19092170 |doi-access=free |issn=1424-8220 |pmc=6539396 |pmid=31083331|bibcode=2019Senso..19.2170T }}</ref>
* '''Environmental Monitoring''': Detecting temperature changes in chemical processes or respiratory systems (e.g., self-powered breathing sensors).<ref name=":0" />

=== Energy Harvesting and Power Generation ===
A pyroelectric can be repeatedly heated and cooled (analogously to a [[heat engine]]) to generate usable electrical power. An example of a  heat engine is the movement of the pistons in an internal combustion engine like that found in a gasoline powered automobile.<ref>{{Cite web |title=Heat engine - Energy Education |url=https://energyeducation.ca/encyclopedia/Heat_engine#:~:text=Internal%20combustion%20engine,-full%20article&text=Internal%20combustion%20engines%20are%20the,is%20then%20emitted%20as%20exhaust. |access-date=2023-09-07 |website=energyeducation.ca |language=en}}</ref><ref name=":0" />

One group calculated that a pyroelectric in an [[Ericsson cycle]] could reach 50% of [[Carnot efficiency]],<ref>{{cite journal | last1 = Sebald | first1 = Gael | last2 = Pruvost | first2 = Sebastien | last3 = Guyomar | first3 = Daniel | title = Energy harvesting based on Ericsson pyroelectric cycles in a relaxor ferroelectric ceramic | journal = Smart Materials and Structures | volume = 17 | issue = 1 | pages = 015012 | year = 2008 | doi = 10.1088/0964-1726/17/01/015012 |bibcode = 2008SMaS...17a5012S | s2cid = 108894876 |url=http://www.ikhebeenvraag.be/mediastorage/FSDocument/135/Pyroelectric+energy+harvesting.pdf}}</ref><ref>{{cite journal | last1 = Sebald | first1 = Gael | last2 = Guyomar | first2 = Daniel | last3 = Agbossou | first3 = Amen | title = On thermoelectric and pyroelectric energy harvesting | journal = Smart Materials and Structures | volume = 18 | issue = 12 | pages = 125006 | year = 2009 | doi = 10.1088/0964-1726/18/12/125006 |bibcode = 2009SMaS...18l5006S | s2cid = 53378208 }}</ref> while a different study found a material that could, in theory, reach 84-92% of Carnot efficiency<ref>{{cite journal | last1 = Olsen | first1 = Randall B. | last2 = Evans | first2 = Diane | title = Pyroelectric energy conversion: Hysteresis loss and temperature sensitivity of a ferroelectric material | journal = Journal of Applied Physics | volume = 54 | issue = 10 | pages = 5941–5944 | year = 1983 | doi = 10.1063/1.331769|bibcode = 1983JAP....54.5941O }}</ref> (these efficiency values are for the pyroelectric itself, ignoring losses from heating and cooling the [[thin film|substrate]], other heat-transfer losses, and all other losses elsewhere in the system)

Possible advantages of pyroelectric generators for generating electricity (as compared to the conventional [[heat engine]] plus [[electrical generator]]) include:

* Harvesting energy from waste-heat:<ref>{{Cite journal |last1=Pandya |first1=Shishir |last2=Velarde |first2=Gabriel |last3=Zhang |first3=Lei |last4=Wilbur |first4=Joshua D. |last5=Smith |first5=Andrew |last6=Hanrahan |first6=Brendan |last7=Dames |first7=Chris |last8=Martin |first8=Lane W. |date=2019-06-07 |title=New approach to waste-heat energy harvesting: pyroelectric energy conversion |journal=NPG Asia Materials |language=en |volume=11 |issue=1 |pages=1–5 |doi=10.1038/s41427-019-0125-y |issn=1884-4057|doi-access=free }}</ref><ref name=":1">{{Cite journal |last1=Mondal |first1=Rajib |last2=Hasan |first2=Md Al Mahadi |last3=Baik |first3=Jeong Min |last4=Yang |first4=Ya |date=2023-06-01 |title=Advanced pyroelectric materials for energy harvesting and sensing applications |url=https://www.sciencedirect.com/science/article/abs/pii/S1369702123000858 |journal=Materials Today |volume=66 |pages=273–301 |doi=10.1016/j.mattod.2023.03.023 |issn=1369-7021}}</ref><ref name=":0" />
** '''Waste Heat Recovery''': Harvesting low-grade thermal energy from industrial processes, automotive systems, and electrical appliances using lead-based ceramics (e.g., PZT, PMN-PT), lead-free ceramics (e.g., BNT-BT, KNN), and polymers (e.g., PVDF-TrFE). The Olsen cycle is a prominent thermodynamic method for efficient energy conversion.
* Less bulky equipment:<ref name=":0" />
** '''Flexible and Wearable Devices''': Flexible polymers (e.g., PVDF) and composites power wearable/implantable electronics by leveraging body heat or ambient temperature changes. Examples include self-powered sensors and nanogenerators producing μW to mW/cm<sup>3</sup> power densities.
* Fewer moving parts.<ref>{{cite journal | last1 = Kouchachvili | first1 = L | last2 = Ikura | first2 = M | title = Pyroelectric conversion—Effects of P(VDF–TrFE) preconditioning on power conversion | journal = Journal of Electrostatics | volume = 65 | issue = 3 | pages = 182–188 | year = 2007 | doi = 10.1016/j.elstat.2006.07.014}}</ref>

Although a few patents have been filed for such a device,<ref>For example: [http://www.freepatentsonline.com/4647836.html US Patent 4647836], [http://www.freepatentsonline.com/6528898.html US Patent 6528898], [http://www.freepatentsonline.com/5644184.html US Patent 5644184]</ref> such generators do not appear to be anywhere close to commercialization.

=== Nuclear fusion ===
{{main|Pyroelectric fusion}}

Pyroelectric materials have been used to generate large electric fields necessary to steer [[deuterium]] ions in a [[nuclear fusion]] process. This is known as [[pyroelectric fusion]].

=== Challenges and Future Directions ===
Despite their promising applications, pyroelectric materials face several challenges that must be addressed for broader adoption. One key limitation is the trade-off between pyroelectric coefficients, dielectric properties, and thermal stability, which affects overall performance and efficiency. Additionally, the efficiency of pyroelectric energy harvesting is highly dependent on rapid temperature fluctuations, making it challenging to achieve consistent power output in practical applications. Integration into flexible and biocompatible designs for wearable and miniaturized devices also remains a significant hurdle. Ongoing research aims to enhance figures of merit (FoMs), optimize phase transitions near morphotropic boundaries, and develop hybrid systems that combine pyroelectricity with other energy-harvesting mechanisms for multifunctional applications. Despite these challenges, the versatility of pyroelectric materials positions them as critical components for sustainable energy solutions and next-generation sensor technologies.<ref name=":1" /><ref name=":0" />