Preparation and properties of Zr2WP2O12 with negative thermal expansion without sintering additives

Abstract

Zirconium tungsten phosphate (Zr2WP2O12 denoted as ZWP) is a negative thermal expansion material which can be used as filler in controlling the thermal expansion coefficient of other materials. In this study, dense ZWP ceramics without any additives was prepared via solid-state reaction method, by milling the as-synthesized powder for different times and sintering at 1300?C. The influence of the milling time, i.e. reduced particle sizes, on properties of the Zr2WP2O12 was investigated. The obtained samples were characterized by X-ray diffraction (XRD) method, scanning electron microscopy (SEM), thermal mechanical analysis (TMA), Raman spectroscopy and Vickers hardness tester. The results showed that the milled powders have high crystallinity with single phase orthorhombic structure. The ZWP ceramics exhibits NTE property with high density. With the increase of milling time the coefficient of thermal expansion changed from ?2.607 ? 10?6 1/K to ?3.914 ? 10?6 1/K. In addition, the grain sizes decrease and the relative density and HV hardness of the obtained ceramics increase confirming that grinding is an effective method to improve the performance of ZWP ceramics.

Negative and Near-Zero Thermal Expansion in A2M3O12 and Related Ceramic Families: A Review

“…Indeed, the lowest density obtained after sintering was 81.5% TD for the powder milled for 2 h, and when the milling time was extended to 96 h, 95.4% TD was reached. The microstructures of ceramics obtained from powder milled for 2 h had larger grains and a higher proportion of pores, while those obtained from the powder milled for 96 h had a reduction in grain size, allowing for further densification (Shi et al, 2020).…”

“…The influence of different ball milling times (2, 12, 24, 48, 72 and 96 h) on Zr 2 WP 2 O 12 powders and also on some physical properties of the sintered bodies has been reported (Shi et al, 2020). The milled powders were uniaxially cold pressed at 30 MPa and the green bodies were conventionally sintered for 4 h at temperatures as high as 1573 K. It was hypothesized that with increasing milling time, the powder mean particle size would diminish and the powder would become less agglomerated, leading to denser Zr 2 WP 2 O 12 ceramics.…”

“…The hardness of samples increased as the samples became denser and had finer microstructure, ranging from approximately 90 HVN (at 81.5% TD) to 180 HVN (at 95.4% TD). In general terms, for a given material, higher density will lead to higher hardness (Shi et al, 2020). (Prisco et al, 2019 (Isobe et al, 2009).…”