Preparation and characterization of Ni–Zn–O ceramics with Y2Ba2Cu2O7 as sintering aids for NTC thermistors
NTC thermistors have broad application prospects, and low-temperature sintering of NTC thermistors is of great significance in reducing sintering costs and is beneficial for preparing multi-layer structured components with lower cost internal electrode conductors. In this work, a low-melting point compound basing on Y 2 Ba 2 Cu 2 O 7 is selected as sintering agent for the preparation of Li-doped Ni–Zn–O (Ni 0.97- x Zn x Li 0.03 O 2 , x = 0.1, 0.3, 0.5, 0.7) ceramic thermistors. The sintering temperature can be reduced by more than 250 °C comparing with the one of the related ceramics without sintering aid (NiO ceramics was sintered at 1400 °C). The fabricated Li-doped Ni–Zn–O ceramics consist of single salt-rock NiO phase for x ≤ 0.3 and are composed of NiO-rich and ZnO-rich phases for x = 0.5 or 0.7. All ceramics show typical NTC characteristics with a wide-range adjustable material constant ( B values ranging from 756 to 4967 K). The Ni–Zn–O ceramics have high aging stability with the resistance shift rates induced at 125 °C lower than 1.89%. The microstructure, conduction modes and aging mechanism were investigated using the XRD, SEM, XPS, and electrochemistry impedance spectra.
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