Negative Thermal Expansion Caused by the Antiferroelectric Phase Transition in Lead-Free Perovskite Ceramics

Due to the structural stability and high adjustability of perovskite, lead-free perovskite ceramics are widely thought to be one of the most promising functional materials. In this work, an abnormal negative thermal expansion behavior with a linear expansion coefficient of −54.95 ppm/K is achieved in the (1-x)NaNbO3-xCaZrO3 system by driving the antiferroelectric phase transition from orthorhombic phase and tetragonal phase. The NTE mechanism is verified by temperature-dependent high-energy synchrotron X-ray diffraction, dielectric spectra, and Raman scattering spectroscopy. The relationship between the antiferroelectric phase transition and negative thermal expansion behavior is systematically revealed by analyzing the evolution of the phase structure with temperature. This novel negative thermal expansion feature caused by the antiferroelectric phase transition provides new guidance for designing more negative thermal expansion materials.