A-site Deficient Neodymium-doped Strontium Titanate as a Possible n-type Thermoelectric Material

Open Access
- Author:
- Lewis, Neal P
- Area of Honors:
- Materials Science and Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Clive A Randall, Thesis Supervisor
Dr. Robert Allen Kimel, Thesis Honors Advisor - Keywords:
- thermoelectricity
energy
thermal conductivity
doped strontium-titanate
ceramics - Abstract:
- There is significant research on lanthanum doped strontium titanate systems for possible thermoelectric applications. However, to fully understand the effects of defect chemistry on thermoelectric properties, there is a need to look at other dopants from the lanthanide series. Additionally, many researchers focus on electronic compensation for doped systems, while there is evidence that ionic compensation can help decrease thermal conductivity in SrTiO3 systems. The goals of this work are to investigate doping SrTiO3 with neodymium, gain a better understanding of the role of strontium deficiencies on thermoelectric properties, and determine the viability of a-site deficient neodymium doped strontium titanate as an n-type thermoelectric material. After executing the necessary experiments, it was found that the substitution of neodymium for strontium played an important role in the Seebeck coefficient. As the neodymium content increased, the Seebeck coefficient decreased in magnitude. However, samples with 10 percent neodymium content produced a significantly large Seebeck coefficient, leading to a power factor comparable to the state-of-the-art-materials. The neodymium content also played an important role in the thermal conductivity. As expected, increasing the neodymium content reduced the thermal conductivity due to the introduction of more A-site vacancies to scatter phonons. Additionally, the reducing atmosphere during sintering resulted in all compositions having near metallic-like electrical conductivities. All of these measurements showed that neodymium doped strontium titanate has high promise as a bulk thermoelectric oxide. The 10 percent neodymium sample exhibited a figure of merit of 0.6 at 973 K, which is competitive with current state-of-the-art n-type thermoelectric materials.