Effect of densification technique and carrier concentration on the thermoelectric properties of n-type Cu1.45Ni1.45Te2 ternary compound,CrystEngComm

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Effect of densification technique and carrier concentration on the thermoelectric properties of n-type Cu1.45Ni1.45Te2 ternary compound
CrystEngComm ( IF 2.6 ) Pub Date : 2020-11-11 , DOI: 10.1039/d0ce01166e
S. Kavirajan _{1,

2,

3,

4,

5} , J. Archana _{1,

2,

3,

4,

5} , S. Harish _{1,

2,

3,

4,

5} , M. Navaneethan _{1,

2,

3,

4,

5} , S. Ponnusamy _{1,

2,

3,

4,

5} , K. Hayakawa _{6,

7,

8,

9} , Y. Kubota _{7,

8,

9,

10} , M. Shimomura _{6,

7,

8,

9} , Y. Hayakawa _{7,

8,

9,

11}

Affiliation

Cu_1.45Ni_1.45Te₂ ternary compound was synthesized by solid-state ball-milling method and densified via spark plasma sintering (SPS) and cold-pressing with annealing (CPA) techniques. The effect of densification techniques on the thermoelectric properties was studied. SPS sample showed negative Seebeck coefficient values for the entire temperature range, while CPA sample changed the sign of the Seebeck coefficient above 573 K from n-type to p-type. The electrical conductivity was higher for SPS sample than for CPA sample for the entire temperature range. Hence, SPS sample exhibited 167% increased zT when compared to CPA sample. It is confirmed that the SPS technique is more suitable to obtain a high zT value than the CPA technique for n-type Cu_1.45Ni_1.45Te₂ sample. Also, the effect of carrier concentration was studied and the change in the carrier concentration was done by Se-doping. From a series of thermoelectric measurements, it was found that the undoped sample exhibited a high zT of about 0.004 at 400 K and the Se-doped sample exhibited a zT of 0.001 at 750 K. It means that Se-doping mainly influences the shifting of the operating temperature of TE performance from room temperature range to mid-temperature range. The formation of n-type TE material was realized due to the delocalization of electron density on Te-ions, which compensate the Cu-vacancies resulting in the n-type conduction behaviour. Se-doping modifies the reaction of Te-ions with cations affecting the delocalization of electron density, which shifts the conduction type from n-type to p-type behaviour.

中文翻译：

致密化工艺和载流子浓度对n型Cu1.45Ni1.45Te2三元化合物热电性能的影响

通过固态球磨法合成Cu _1.45 Ni _1.45 Te ₂三元化合物，并通过火花等离子体烧结（SPS）和退火冷压（CPA）技术进行致密化。研究了致密化技术对热电性能的影响。SPS样品在整个温度范围内均显示负的塞贝克系数值，而CPA样品将573 K以上的塞贝克系数的符号从n型更改为p型。在整个温度范围内，SPS样品的电导率高于CPA样品的电导率。因此，与CPA样品相比，SPS样品的zT增加了167％。可以肯定的是，SPS技术更适合于获得较高的对于n型Cu _1.45 Ni _1.45 Te ₂样品，zT值高于CPA技术。另外，研究了载流子浓度的影响，并且通过Se掺杂完成了载流子浓度的变化。通过一系列热电测量，发现未掺杂的样品在400 K时表现出约0.004的高zT，而硒掺杂的样品表现出zT在750 K时为0.001。这意味着Se掺杂主要影响TE性能的工作温度从室温范围转变为中温范围。n型TE材料的形成是由于电子离子在Te离子上的离域而实现的，这可以补偿Cu空位，从而导致n型导电行为。硒掺杂会改变Te离子与阳离子的反应，从而影响电子密度的离域，从而将导电类型从n型转变为p型。

更新日期：2020-11-12

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