TY - JOUR
T1 - Influence of bismuth oxide as a sintering aid on the densification of cold sintering of zirconia
AU - Bhootpur, Nikhil
AU - Brouwer, Hans
AU - Tang, Yinglu
PY - 2023
Y1 - 2023
N2 - In the past decades, Zirconia (ZrO2) has emerged as a promising technical ceramic, both as high temperature structural material and electrolyte for fuel cells, etc. The traditional synthesis of ZrO2 with spark plasma sintering (SPS) usually requires a sintering temperature as high as 1200 °C. General interest in lowering the sintering temperature to reduce energy consumption and thermal stresses has led to research on two promising routes – cold sintering via temperature-dependent chemical reactivity and sintering aids, which facilitates mass transport and improves densification. Here we combine both by developing a single-step sintering process benefitting from both water vapor through the in-situ conversion of Zr(OH)4 to ZrO2 and liquid phase Bi2O3 as a sintering aid. The resultant ZrO2 has a relative density above 80% with a sintering temperature as low as 900 °C, significantly higher than that of ZrO2 without sintering aids, which had a relative density of 54%, both sintered at 50 MPa. The dependence of porosity of sintered samples as a function of sintering pressure (range: 50 MPa–300 MPa) and temperature (range 400 °C–1200 °C) is mapped out as guidance for further material property design. A linear relationship between hardness and relative density was found, with a maximal hardness of 6.6 GPa achieved in samples with 30% porosity. In addition to sintered density, phase stabilization of tetragonal ZrO2 is enhanced at sintering temperature of 900 °C with water vapor and Bi2O3, respectively.
AB - In the past decades, Zirconia (ZrO2) has emerged as a promising technical ceramic, both as high temperature structural material and electrolyte for fuel cells, etc. The traditional synthesis of ZrO2 with spark plasma sintering (SPS) usually requires a sintering temperature as high as 1200 °C. General interest in lowering the sintering temperature to reduce energy consumption and thermal stresses has led to research on two promising routes – cold sintering via temperature-dependent chemical reactivity and sintering aids, which facilitates mass transport and improves densification. Here we combine both by developing a single-step sintering process benefitting from both water vapor through the in-situ conversion of Zr(OH)4 to ZrO2 and liquid phase Bi2O3 as a sintering aid. The resultant ZrO2 has a relative density above 80% with a sintering temperature as low as 900 °C, significantly higher than that of ZrO2 without sintering aids, which had a relative density of 54%, both sintered at 50 MPa. The dependence of porosity of sintered samples as a function of sintering pressure (range: 50 MPa–300 MPa) and temperature (range 400 °C–1200 °C) is mapped out as guidance for further material property design. A linear relationship between hardness and relative density was found, with a maximal hardness of 6.6 GPa achieved in samples with 30% porosity. In addition to sintered density, phase stabilization of tetragonal ZrO2 is enhanced at sintering temperature of 900 °C with water vapor and Bi2O3, respectively.
KW - Low temperature (cold) sintering
KW - Sintering aid
KW - Spark plasma sintering
KW - Zirconium hydroxide
UR - http://www.scopus.com/inward/record.url?scp=85168383007&partnerID=8YFLogxK
U2 - 10.1016/j.ceramint.2023.07.207
DO - 10.1016/j.ceramint.2023.07.207
M3 - Article
AN - SCOPUS:85168383007
SN - 0272-8842
VL - 49
SP - 33495
EP - 33499
JO - Ceramics International
JF - Ceramics International
IS - 21
ER -