"JNCASR Researchers Shatter Thermoelectric Limit in Crystalline Semiconductor"
Seebeck Effect
generation of voltage across dissimilar materials when a temperature difference is applied across their junction.
Seebeck Coefficient
voltage generated per unit temperature difference; measured in volts per Kelvin; quantifies thermoelectric performance.
The Seebeck effect, discovered two centuries ago, describes how a temperature difference across a junction of two dissimilar materials drives mobile charge carriers from the hot side to the cold side, generating a measurable voltage. The magnitude of this voltage per unit temperature difference is called the Seebeck coefficient. This effect underlies a wide range of practical technologies: thermocouple temperature sensors, thermoelectric generators that recover waste heat, and infrared detectors.
For decades, solid-state physics established a firm upper bound on the Seebeck coefficient in crystalline solids. Most metals produce only tens of microvolts per Kelvin. Even high-performance semiconductors rarely exceed a few hundred microvolts per Kelvin. Only liquid systems, ionic gels and electrolytes, where charged ions (not electrons) carry heat, were known to cross into the millivolts-per-Kelvin range. This boundary was treated as a fundamental limit of solid-state thermoelectrics, rooted in the Boltzmann transport framework that governs electron movement in ordered crystals.
India's Department of Science and Technology (DST) funds a network of autonomous research institutes that work at the frontier of materials science. The Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, is one such institute. Its collaboration with the Indian Institute of Science (IISc), Bengaluru, and the University of Sydney on this discovery reflects the growing role of Indian institutions in globally significant basic-science breakthroughs.
The central concept here is the heavily doped, highly compensated (HDHC) semiconductor. In a conventional semiconductor, doping introduces either extra electrons (n-type) or electron vacancies (p-type). In an HDHC material, both positively and negatively charged dopant atoms are introduced in nearly equal numbers. The result is a crystal that is electrically compensated, the free carriers largely cancel out, but internally disordered at the atomic scale, even though the overall crystal structure remains intact.
The JNCASR team grew thin films of scandium nitride (ScN), a refractory transition-metal nitride, on magnesium oxide substrates using ultrahigh-vacuum magnetron sputtering. They doped the films with magnesium to compensate ScN's naturally occurring free electrons from oxygen dopants. X-ray diffraction and atomic-resolution electron microscopy confirmed that the films remained single-crystalline and epitaxial, meaning the crystal lattice was continuous and defect-free at the macroscopic level, even as dopant atoms were distributed randomly throughout. …
With reference to radioisotope thermoelectric generators (RTGs), consider the following statements:
1.RTGs are miniature fission reactors.
2.RTGs are used for powering the onboard systems of spacecrafts.
3.RTGs can use Plutonium-238, which is a by-product of weapons development.
Which of the statements given above are correct?
Which one of the following is the context in which the term "qubit" is mentioned?
Discuss the work of 'Bose-Einstein Statistics' done by Prof. Satyendra Nath Bose and show how it revolutionized the field of Physics.
Consider the following statements regarding the Seebeck effect and thermoelectric materials:
1.The Seebeck coefficient measures the electrical voltage generated per unit temperature difference in a material.
2.In conventional crystalline semiconductors, the Seebeck coefficient typically exceeds 100 millivolts per Kelvin.
3.Liquid electrolytes and ionic gels were previously the only systems known to achieve millivolts-per-Kelvin thermoelectric response.
4.Radioisotope Thermoelectric Generators (RTGs) used in spacecraft exploit the Seebeck effect.
How many of the above statements are correct?
With reference to the recent discovery of anomalously large thermoelectric response in scandium nitride (ScN) films, consider the following statements:
1.The films were grown using ultrahigh-vacuum magnetron sputtering on magnesium oxide substrates.
2.The material is classified as a heavily doped, highly compensated (HDHC) semiconductor.
3.The discovery was made by researchers at the Indian Institute of Technology (IIT), Delhi.
4.The Seebeck coefficient measured exceeded –124 millivolts per Kelvin near room temperature.
Which of the statements given above are correct?
Match the following thermoelectric/quantum concepts with their correct descriptions:
List I (Concept) — List II (Description)
A.Seebeck effect — 1. Statistical framework describing indistinguishable integer-spin particles
B.Boltzmann limit — 2. Voltage generation from a temperature difference across dissimilar materials
C.Bose-Einstein Statistics — 3. Theoretical ceiling on Seebeck coefficient in crystalline solids
D.RTG — 4. Spacecraft power device using radioactive decay heat and thermoelectric conversion
Select the correct answer using the codes below:
Which of the following best explains why the heavily doped, highly compensated (HDHC) scandium nitride semiconductor achieves an anomalously large Seebeck coefficient?
Consider the following statements about the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR):
1.It is an autonomous institute under the Department of Science and Technology (DST).
2.It is located in Bengaluru.
3.It is a statutory body established by an Act of Parliament.
Which of the statements given above is/are correct?
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