Cold sintering of calcite: A low‐temperature method for the fabrication of artificial marble

This study presents a novel approach for the low-temperature fabrication of dense calcite (CaCO3) without the use of a carbon dioxide (CO2) atmosphere. CaCO3 powder was cold sintered (390 MPa, 150°C) using distilled water as a transient liquid, followed by heat treatment at 350°C (lower than the decomposition temperature of CaCO3) for 5 hours. The resulting ceramics achieved a relative density of 95 ± 1%, compared to 76 ± 2% prior to heat treatment and 78 ± 2% for conventionally sintered samples. An optimum hardness (134 ± 24 MPa) equivalent to artificial marble was achieved after heat treatment at 350°C, indicating effective densification and strong interparticle bonding. X-ray diffraction and Raman spectroscopy confirmed the retention of the calcite phase, with no evidence of aragonite or vaterite, demonstrating phase stability. Scanning electron microscopy micrographs revealed a dense microstructure with minimal porosity and well-developed grain contacts, consistent with the improved mechanical performance. These results highlight the potential of cold sintering as a sustainable, low-temperature, and binder-free route for fabricating dense and mechanically robust CaCO3 ceramics.