Remarkably improved nonlinearity and thermal stability of CaYNbMnO₇ thermosensitive ceramics via the cold-sintering process

The cold-sintering process (CSP) uses a transient low-temperature solvent, such as water or water with dissolved solutes consistent with the ceramic composition, to achieve functionalization at lower temperatures via the dissolution and precipitation principle. Here, during the CSP, the use of molten NaOH as a flux solvent promoted the rearrangement and precipitation of CaYNbMnO7 particles. CaYNbMnO7 ceramics were successfully obtained at 350 degrees C and under a uniaxial pressure of 700 MPa. The ceramic was not a single-phase structure but consisted of a cubic-phase structure and a layered perovskite structure. To verify the high-temperature thermal stability of CaYNbMnO7 ceramic prepared at 350 degrees C, a comparative study was conducted with conventional sintering (CS). Results indicate that the ceramics obtained by CSP and CS have negative temperature coefficient characteristics. The cold-sintered ceramic has a wider temperature range and better aging stability. (The minimum value of the aging coefficient is similar to 2.49%.) Simultaneously, CSP is beneficial for promoting the linearization of the relationship between the logarithm in the resistivity (ln rho) and the reciprocal for the absolute temperature (1000/T) in the ceramic. However, the CSP has little effect on the material constant B and thermal activation energy Ea of the ceramic, providing a basis for the low-temperature synthesis of high melting point thermosensitive ceramics.