Seebeck coefficient of Ca2.8Pr0.2Co4O9 synthesized by sol-gel method with thermal and structural characterization*

Abstract

 Bu çalışmada, yüksek sıcaklıktaki termoelektrik jeneratör uygulamaları için Ca2.8Pr0.2Co4O9 tozları sol-jel metodu ile sentezlenmiş, tozların ısıl ve yapısal karakterizasyonu sistematik olarak incelenmiştir. Kalsinasyon işlemi için, tozların uygun ısıl rejimlerinin belirlenmesinde Diferansiyel Termal Analiz-Termogravimetri (DTA-TG) kullanılmıştır. Orta sıcaklık ürünlerinin reaksiyon türü ve kimyasal yapısı Fourier Dönüşümlü Kızılötesi Spektrometresi (FTIR) ile tanımlanmıştır. Tozların yapısal özellikleri X-Işınları Kırınımı (XRD) ile gerçekleştirilmiş ve tozların içerisinde bulunan elementlerin kimyasal kompozisyonunun ve deneysel formülünün belirlenmesinde X-Işınları Fotoelektron Spektroskopisi (XPS) kullanılmıştır. Faz spektrumuna bakıldığında Ca2.8Pr0.2Co4O9'in 2θ piklerinin tipik Ca3Co4O9 pikleri ve literatürle uyuştuğu görülmektedir. Numunelerin Seebeck katsayıları Ca2.8Pr0.2Co4O9'in literatür değerlerine yakın, aynı zamanda Ca3Co4O9'in değerlerinden daha yüksektir. Ca2.8Pr0.2Co4O9 için en yüksek Seebeck katsayısı değeri 400 °C'de 179 µV/K olarak bulunmuştur ve bu değer literatür değerinden bir miktar daha yüksektir. Bu sonuçlar, Pr'un, Seebeck katsayısı değerinin artırılmasında etkili bir katkı olduğunu göstermektedir. 

Keywords

• Seebeck katsayısı,sol-jel metodu,oksit termoelektrik malzemeler,ısıl analiz

Seebeck Coefficient of Ca2.8Pr0.2Co4O9 Synthesized by Sol-Gel Method with Thermal and Structural Characterization

Abstract

In this paper, Ca2.8Pr0.2Co4O9 powders were synthesized by sol-gel method and thermal and structural characterization of the powders were systematically examined for high temperature thermoelectric generator applications. Differential Thermal Analysis-Thermogravimetry (DTA-TG) was used to specify appropriate thermal regime of the powders for calcination process. Chemical structure and reaction type of intermediate temperature products were defined by Fourier Transform Infrared (FTIR) Spectroscopy. Structural properties of the powders were implemented by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) was used to specify chemical composition and empirical formula of the elements existed within the powders. It can be seen from the phase spectrum that 2θ peaks of Ca2.8Pr0.2Co4O9 correspond to the literature and coincide with typical Ca3Co4O9 peaks. Seebeck coefficients of the samples are much higher than Ca3Co4O9 while they are closer to literature value of Ca2.8Pr0.2Co4O9. The highest Seebeck coefficient of Ca2.8Pr0.2Co4O9 is found to be 179 µV/K at 400 °C which is a little higher than the literature value. These results show that Pr is an effective dopant to increase the Seebeck coefficient values.

Keywords

• Seebeck coefficient,sol-gel process,oxide thermoelectrics,thermal analysis

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