Investigation of the thermal shrink mechanism,thermal conductivity and compressive resistance of TaTiP3O12 ceramics

Dense TaTiP₃O₁₂ ceramics were synthesized by the solid-state method and spark plasma sintering (SPS) with 6 wt% V₂O₅ as a sintering aid, and their phase, microstructure, thermal conductivity, hardness, compressive strength, and expansion property and mechanism were investigated. Results show that the pure phase can be achieved by the two methods. In particular, the sample prepared by SPS possesses a relative density of 97.62% and a porosity of 3.07%, and has better properties than that prepared by the solid-state method. The SPS sample has a thermal conductivity at room temperature of 2.03 w/(m· °C), a Vickers hardness of 4.34 GPa and a compressive strength of 175.98 MPa, which are 0.95, 1.49 and 1.59 times greater than those of the sample prepared by the solid-state method, respectively. In addition, the TaTiP₃O₁₂ ceramic prepared by SPS exhibits a linear ultralow negative thermal expansion property with a coefficient of thermal expansion of ?0.74 × 10^?6 °C ^?1 (-100–400 °C). The negative thermal expansion in TaTiP₃O₁₂ is induced by the coupling effect of Ta(Ti)O₆] octahedron and PO₄] tetrahedron caused by the transverse vibration of bridging oxygen atoms.