Properties of negative thermal expansion β-eucryptite ceramics prepared by spark plasma sintering**Project supported by the Programs for Tackling Key Problems in Science and Technology, Henan Province, China (Grant Nos. 172102210103, 182102310895, 182102210031, and 182102311079), the Doctoral Program of Henan Institute of Engineering, China (Grant Nos. D2016015 and D2016016), and the Nationallevel College Students Innovative Entrepreneurial Training Plan Program, China (Grant

Abstract

β-eucryptite powders are prepared by the sol–gel method through using tetraethoxysilane lithium nitrate and aluminum isopropoxide as starting materials. β-eucryptite ceramics are prepared by spark plasma sintering. The effects of sintering temperature on the negative thermal expansion properties of the β-eucryptite are investigated by x-ray diffraction (XRD), scanning electron microscopy, and thermal expansion test. The XRD results exhibit no change in the crystal structure of the sample prepared by different sintering processes. The negative thermal expansion properties increase with the increase of the sintering temperature. The coefficient of thermal expansion of β-eucryptite ceramics sintered at 1100 °C is calculated to be −4.93 × 10−6 °C−1. Crystallization behaviors of the ceramics may play an important role in the increase of negative thermal expansion of β-eucryptite. High sintering temperature could improve the crystallization behaviors of the ceramics and reduce the residue glass phase, which can improve the negative thermal expansion properties of β-eucryptite ceramics.