Improvement of thermoelectric properties of MnSi thermodetectors byultrasound processing

T.C.Kamilov¹, R.A. Muminov², B.N. Zaveryukhin²,S.Zh. Karazhanov², N.N. Zaveryukhina¹, B.C. Kamilov¹

¹TashkentAviation Institute, 12 Akhunbabaev St., 700047, Uzbekistan

²Physical-TechnicalInstitute, 2B Mavlyqanov St, Tashkent, 700084, Uzbekistan

This work presents aninvestigation of the effect of ultrasound on thermoelectric properties of MnSibased films, converters and IR-detectors of thickness in the range from 1 to 20mm. Basic parameters of the films have beenstudied for the temperature range from 400 to 1000 K. Conversion factor (S) andthermoelectromotive force (a) were in the range from 500 to 1000mV/W and 150 to 250 mV/K,respectively, in the temperature range from 223 to 1000 K. Response time (t) was equal to 10^-6 s.

The devices have beenprocessed by ultrasound of frequency 3.5 MHz and of intensity 1 W/cm2 for 45minutes at T=240 K. As a result, the thermoelectric force coefficient has beenincreased significantly from the above range to a=360 ¸ 400 mV/K, while the conversion factor wasincreased to ~80 %.

The changes of theoutput parameters are suggested to be the result of ultrasound induced changesof electrophysical properties of the intergrain region because of the columnarstructure of the films. In the region the dangling bonds can cause the increaseof the density of states at the grain boundaries and are closely related toeffective thermal conductivity of the grains. Due to the ultrasound processingthermal conductivity of the grain decreases, which can result in the increaseof thermoelectromotive force. So, the ultrasound processing can be consideredas one of the approaches, which can help to optimize the output parameters ofthe devices.