Prelims: Current events of national and international importance | Science & Technology.
Why in News?
Recently, Scientists from JNCASR, IISc & University of Sydney discovered a crystalline semiconductor that generates thermoelectric voltage far beyond the accepted limit.
- Seebeck effect – It is the creation of an electrical voltage when two different metals or semiconductors have one end heated and the other end cooled.
- Principle of Operation
- Temperature Difference – Heat is applied to one junction of two joined, dissimilar materials, while the opposite junction remains at a lower temperature.
- Electron Movement – Free electrons within the materials acquire thermal energy and exhibit increased mobility at the heated junction.
- Voltage Generation – These fast-moving electrons diffuse toward the cooler side, creating a charge separation and a measurable voltage, known as the Seebeck voltage.
- Previous Scientific Limitations – Historically, scientists considered the practical upper limit for crystalline solid materials to be only a few millivolts per Kelvin.
- Metals – It typically exhibit Seebeck coefficients in the range of tens of microvolts per Kelvin (μV/K).
- High-quality semiconductors – These are generally display Seebeck coefficients in the hundreds of microvolts per Kelvin (μV/K).
- Certain liquid electrolytes and ionic systems – These can reach Seebeck coefficients in the millivolts per Kelvin (mV/K) range.
- Recent Breakthrough – Modified scandium nitride (ScN) has demonstrated a Seebeck coefficient exceeding the previously established limits:
- Specifically, a value of −124.6 millivolts per Kelvin (mV/K) was observed near room temperature.
- This value significantly surpasses the previously accepted upper limit for crystalline inorganic solids.
How was this scientific outcome achieved?
- The researchers utilized Scandium Nitride (ScN) as the base material.
- Magnesium dopants were intentionally introduced into the ScN.
Doping is the intentional introduction of a small quantity of another element to alter the electrical properties of a semiconductor.
- The combination of ScN and magnesium results in heavy doping and charge compensation.
- This process produces a material known as HDHC (Heavily Doped, Highly Compensated) semiconductor.
Reference
PIB | Century-Old Limit on Turning Heat into Electricity
