TY - JOUR
T1 - Continuous functionally graded material to improve the thermoelectric properties of ZnO
AU - Cramer, Corson L.
AU - Gonzalez-Julian, Jesus
AU - Colasuonno, Paul S.
AU - Holland, Troy B.
N1 - Publisher Copyright:
© 2017 Elsevier Ltd
PY - 2017/12
Y1 - 2017/12
N2 - Functionally graded material (FGM) in terms of grain size gradation is fabricated from ZnO with a combination of modified Spark Plasma Sintering (SPS) graphite tooling, water sintering enhancements through transient liquid phase surface transport, and strategic SPS mechanical loading. The grain size gradation of the ZnO FGM spans from 180 nm grains to 1.2 micrometers in a fully dense material. This is the first semiconductor or ceramic to be graded microstructurally to this extent. Predictions of the microstructure with a Master Sintering Curve (MSC) approach were done with a series of isothermal experiments on two different FGM conditions revealing a slight offset due to a constrained mechanism. The mechanical properties were tested with Vickers micro hardness across the sample, showing a gradient in hardness from 2.6 GPa to 4.2 GPa. In addition, the thermoelectric properties of the FGM were measured and show a zT of 2 × 10−5 at 100 °C compared to uniform small- and large-grained samples of 1 × 10−6. This is an order of magnitude difference making a new path for improvements of bulk thermoelectric material.
AB - Functionally graded material (FGM) in terms of grain size gradation is fabricated from ZnO with a combination of modified Spark Plasma Sintering (SPS) graphite tooling, water sintering enhancements through transient liquid phase surface transport, and strategic SPS mechanical loading. The grain size gradation of the ZnO FGM spans from 180 nm grains to 1.2 micrometers in a fully dense material. This is the first semiconductor or ceramic to be graded microstructurally to this extent. Predictions of the microstructure with a Master Sintering Curve (MSC) approach were done with a series of isothermal experiments on two different FGM conditions revealing a slight offset due to a constrained mechanism. The mechanical properties were tested with Vickers micro hardness across the sample, showing a gradient in hardness from 2.6 GPa to 4.2 GPa. In addition, the thermoelectric properties of the FGM were measured and show a zT of 2 × 10−5 at 100 °C compared to uniform small- and large-grained samples of 1 × 10−6. This is an order of magnitude difference making a new path for improvements of bulk thermoelectric material.
KW - Differential constrained sintering
KW - Functionally graded material
KW - Thermoelectrics
UR - http://www.scopus.com/inward/record.url?scp=85025827547&partnerID=8YFLogxK
U2 - 10.1016/j.jeurceramsoc.2017.07.019
DO - 10.1016/j.jeurceramsoc.2017.07.019
M3 - Article
AN - SCOPUS:85025827547
SN - 0955-2219
VL - 37
SP - 4693
EP - 4700
JO - Journal of the European Ceramic Society
JF - Journal of the European Ceramic Society
IS - 15
ER -