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See the supplementary material for the information including (1) Additional ex-perimental details; (2) Microstructure and thermal conductivity versus temperature curves; (3) Three-point bending strain-stress curves; (4) The XRD of composites; (5) Scanning electron microscope elemental distributions of the HT5-treated P32 compo-site; (6) Shift of phase transition temperature of Cu2P2O7 under pressure; (7) ΔL/L(T) curves recorded upon heating during three thermal cycles between 240 K and 350 K for the as-cast P32 and the ones treated by different heat treatments; (8) The different heat treatment process conditions and designations; (9) Theoretical modeling calcula-tions of TC and CTE.