We use cookies to enhance your experience. By continuing to browse this site you agree to our use of cookies. More info.
This article discusses the changes in the behavior of strontium titanate (SrTiO3) ceramics, specifically in their thermoelectric properties and crystal structure, after being doped with different elements such as niobium (Nb), tantalum (Ta), and lanthanum (La) in the context of thermoelectric power generation.
Image Credit: Isacco/Shutterstock.com
Thermoelectric materials have gained considerable attention for harvesting energy from the waste heat liberated from electronic devices, industries, automobiles, and power plants.
The thermoelectric material efficiency is measured by the dimensionless thermoelectric figure of merit ZT = S2 σTқ-1, where σ refers to electrical conductivity/ S cm-1, S is the Seebeck coefficient/ µVK-1, қ is the thermal conductivity/ Wm-1K-1, T is the absolute temperature/K, and Z is the figure of merit.
However, achieving a high ZT is challenging owing to the interdependence of σ, қ, and S. To attain a high ZT, the thermoelectric material must possess a high power factor/S2σ value and a low thermal conductivity.
Typically, the Seebeck coefficient or electrical conductivity is enhanced by nano/micro structuring or doping approaches to increase the power factor of the thermoelectric material.
A range of compounds of potential thermoelectric properties in a large temperature range can be synthesized by doping perovskite-type cubic SrTiO3. The SrTiO3-based oxide thermoelectric materials have gained prominence owing to their low cost, non-toxicity, and excellent redox flexibility and thermal stability.
Undoped SrTiO3 acts as an insulator, which can be converted into a semiconductor by doping pentavalent elements in the B-site and trivalent elements in the A-site. The donor dopant with a higher cationic charge, such as Ta5+ and Nb5+, replaces the host cation titanium (Ti4+) with a lower charge in the doping process, which brings either more electrons or ions into the system compared to the host oxide and improves the electrical properties of SrTiO3 ceramics.
A paper recently published in the journal Materials Today: Proceedings demonstrated changes in the thermoelectric properties and the structure of SrTiO3 ceramics after the ceramics were doped with Nb/Ta or co-doped with Nb and Ta.
The lattice constant was increased in the Ta/Nb-doped SrTiO3 compared to undoped SrTiO3 due to the higher ionic radii of Ta and Nb dopants compared to the replaced host Ti atom.
However, the lattice constant remained the same in the Nb-Ta co-doped and Nb/Ta doped SrTiO3 owing to the similar ionic radii of both Nb and Ta. The tolerance factor and unit cell volume of Nb/Ta substituted and co-doped SrTiO3 also displayed no difference due to the same ionic radii of dopants.
The thermoelectric properties, such as the Seebeck coefficient and electrical conductivity, were evaluated in an inert atmosphere to prevent the reoxidation of the doped SrTiO3 samples at extremely high temperatures.
In all doped samples, the electrical conductivity decreased with an increasing temperature, indicating the general metallic behavior of the Nb/Ta substituted and co-doped SrTiO3 ceramics.
However, the Nb-doped SrTiO3 samples displayed a typical semiconductor behavior as the electrical conductivity increased in Nb-doped SrTiO3 samples till 570 K. In the Ta-doped SrTiO3 samples, the electrical conductivity decreased consistently with the increasing temperature, which improved the metallicity of the samples.
Ta-Nb co-doped samples with an equal concentration of both dopants displayed the highest electrical conductivity of 235 S cm-1 at 470 K due to the creation of more charged carriers compared to other doped samples.
Unlike the electrical conductivity, the Seebeck coefficient was increased in correspondence with the increasing temperature. The inverse relationship between the Seebeck coefficient and electrical conductivity resulted in a higher electrical conductivity when the Seebeck coefficient value was low. The Ta doping decreased the Seebeck coefficient value, while Nb doping increased the value in the samples.
In Ta doped samples, the Seebeck coefficient decreased considerably while the electrical conductivity was enhanced, indicating that the increase in the number of charge carriers in Ta doping was due to the increased oxygen vacancies. The highest Seebeck coefficient value of 190 µVK-1 was observed at 1080 K for Nb-doped SrTiO3 samples.
The power factor values increased with the rising temperature in all samples. Although the Ta and Nb co-doped samples demonstrated the highest electrical conductivity, their power factor values decreased with the rising concentration of Ta, owing to the substantial decrease in the Seebeck coefficient. The maximum power factor value of 250 µWm-1K-2 was observed at 900 K in the Nb-doped SrTiO3 samples.
In another study published in the journal Chemistry of Materials, researchers investigated the thermoelectric properties and structure of lanthanum (La)-doped A-site-deficient SrTiO3 (Sr1−3x/2LaxTiO3) ceramics sintered in nitrogen/5%hydrogen and air.
The optimized ZT values of 0.41 obtained for n-type Sr1 −3x/2LaxTiO3‑δ ceramics at 973 K with 0.125 ≤ x ≤ 0.175 was the highest reported thermoelectric ZT values for any perovskite-based SrTiO3 ceramics.
The high ZT values were achieved by the close control of ceramic processing conditions and careful selection of starting compositions, which created defective perovskite lattices consisting of O- and A-site vacancies with mixed valent Ti4+ and Ti3+ on the B-site.
Although the optimized materials featured highly defective nonstoichiometric perovskites, they were resistant to rapid reoxidation in the air at temperatures up to 1273 K, which showed their potential in thermoelectric application such as n-type legs in thermoelectric generators.
To summarize, the doping approach has been found suitable for effectively improving the thermoelectric properties of perovskite-type cubic SrTiO3. Thus, the approach can be potentially implemented for the synthesis of efficient thermoelectric materials with a high figure of merit.
More from AZoM: Use and Applications of Flame Atomic Absorption Spectroscopy
Charan Prasanth S., Jose, R., Vijay, A., Vineetha P., Venkata Saravanan K. Tuning thermoelectric properties of Nb and Ta co-doped SrTiO3 ceramics. Materials Today: Proceedings. ISSN 2214-7853. 2022. https://doi.org/10.1016/j.matpr.2022.04.908
Lu, Z., Zhang, H., Lei, W., Sinclair, D.C., and Reaney, I. M. High-Figure-of-Merit Thermoelectric La-Doped A-Site-Deficient SrTiO3 Ceramics. Chemistry of Materials. 28, 3, 925–935. 2016. https://doi.org/10.1021/acs.chemmater.5b0461
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.
Samudrapom Dam is a freelance scientific and business writer based in Kolkata, India. He has been writing articles related to business and scientific topics for more than one and a half years. He has extensive experience in writing about advanced technologies, information technology, machinery, metals and metal products, clean technologies, finance and banking, automotive, household products, and the aerospace industry. He is passionate about the latest developments in advanced technologies, the ways these developments can be implemented in a real-world situation, and how these developments can positively impact common people.
Please use one of the following formats to cite this article in your essay, paper or report:
Dam, Samudrapom. (2022, May 27). Considering the Behavior of Doped SrTiO3 Ceramics. AZoM. Retrieved on May 27, 2022 from https://www.azom.com/article.aspx?ArticleID=21714.
Dam, Samudrapom. "Considering the Behavior of Doped SrTiO3 Ceramics". AZoM. 27 May 2022. <https://www.azom.com/article.aspx?ArticleID=21714>.
Dam, Samudrapom. "Considering the Behavior of Doped SrTiO3 Ceramics". AZoM. https://www.azom.com/article.aspx?ArticleID=21714. (accessed May 27, 2022).
Dam, Samudrapom. 2022. Considering the Behavior of Doped SrTiO3 Ceramics. AZoM, viewed 27 May 2022, https://www.azom.com/article.aspx?ArticleID=21714.
Do you have a review, update or anything you would like to add to this article?
In this interview, AZoM talks to Chris Aylott, Senior Engineer at Newcastle University, about fatigue testing in the development of low carbon transport solutions.
AZoM speaks with Dr. Nicola Ferralis from MIT about his research that has developed a low-cost process of creating carbon fibers from hydrocarbon pitch. This research could lead to the large-scale use of carbon fiber composites in industries that have thus far been limited.
In this interview, AZoM speaks with Marco Enger, Senior Tribologist from GGB, to discuss how nano fillers affect transfer films within tribological systems.
This product profile outlines the Versa Flex Checkweighers from Thermo Fisher Scientific.
The LQA 300 FT-IR wine analyzer combines performance, accuracy, ease-of-use, and speed for the analysis of finished wine, must and must under fermentation samples in less than 45 seconds—all in one compact solution.
The SpectraStar™ XT-R Benchtop NIR can analyze virtually any sample type in less than a minute, including solid, slurry, or liquid samples.
This article provides an end-of-life assessment of lithium-ion batteries, focusing on the recycling of an ever-growing amount of spent Li-Ion batteries in order to work toward a sustainable and circular approach to battery use and reuse.
Corrosion is the degradation of an alloy caused by its exposure to the environment. Corrosion deterioration of metallic alloys exposed to the atmosphere or other adverse conditions is prevented using a variety of techniques.
Due to the ever-increasing demand for energy, the demand for nuclear fuel has also increased, which has further created a significant increase in the requirement for post-irradiation examination (PIE) techniques.
AZoM.com - An AZoNetwork Site
Owned and operated by AZoNetwork, © 2000-2022