New negative temperature coefficient ceramics in ACu 3 Ti 4 O 12 (A = Sr, La 2/3 , Ca, Y 2/3 ) system

In this work, new ACu 3 Ti 4 O 12 (A = Sr, La 2/3 , Ca, Y 2/3 ) negative temperature coefficient (NTC) ceramics have been successfully fabricated by traditional solid-state reaction method. XRD analysis shows that the ACu 3 Ti 4 O 12 ceramics are of the CaCu 3 Ti 4 O 12 phase with body-centered cubic structure, suggesting that the change of A-site ion does not change the crystal structure. The scanning electron microscope image shows that the difference of A-site ion in ACu 3 Ti 4 O 12 results in the different micromorphology. The X-ray photoelectron spectroscopy analysis further confirms the coexistence of Cu + /Cu 2+ and/or Ti 3+ /Ti 4+ in the compounds, which are one of the important factors for the electrical conductivity in ACu 3 Ti 4 O 12 ceramics. Electrical performance analysis proves that the effect of grain size on resistivity is greater than that of the A-site ion species. The resistivity decreases with increasing temperature from 25 to 500 °C, indicative of NTC characteristics.