Electrical Conductivity And Thermal Sensitivity Of Doping Modified CuO-based Ceramics

CuO,as a sort of transition metal oxide semiconductor,has the advantage of narrow bandgap,high storage and nontoxicity,and has been widely applied in a series of areas including batteries,catalytics and superconductors,etc..However,its performances in these areas are restricted by its relatively poor electrical conductivity.Therefore,enchancing the electric conductivity of CuO is a key project in associated areas.Meanwhile,semiconductors basing on single-cation oxide possess the advantage of highly adjustable room-temperature resistivity(ρ₂₅)and resistance-temperature coefficients by element doping.This endows them great potential for developing advanced negative-temperature-coefficient（NTC）thermostat.This thesis focus on its application on low-resistance electric devices and frontier NTC thermosensitive ceramics and aims to manipulateρ₂₅and resistance-temperature features of CuO-based ceramics by element doping and study the influence of dopants on the phase component and electrical characteristics.The main work of this thesis is as follows:（1）CuO-based ceramics doped by equivalent ion Sr²⁺(Cu_1-xSr_xO,0≤x≤0.1)were synthesized via a traditional solid reaction method.The influence of Sr²⁺on the microstructure and electric conductivity of CuO-based ceramics are investigated.The Sr²⁺-doped CuO-based ceramics are comprised of major phase of monoclinic CuO and second phase Sr₁₄Cu₂₄O₄₁.Doping of Sr²⁺decreases theρ₂₅of CuO-based ceramics distinctly.ρ₂₅droped monotonously with the increase of x,and changed from 114.18 kΩ·cm for x=0 to 2.70Ω·cm for x=0.1.The electric-conductive mechanism of CuO-based ceramic system was discussed basing on the crystal and conductive characteristic of Sr₁₄Cu₂₄O₄₁.（2）Ti⁴⁺modified Cu_0.99Sr_0.01O(Cu_0.99Sr_0.01O·x Ti O₂,0≤x≤0.07)ceramics were prepared via traditional solid reaction method.Their electric conductivity,thermosensitivity and aging stability are studied combining the characterization of phase component,microstructure and electric features.Apart from main monoclinic phase of CuO,a perovskite-strctured second phase formed in Ti⁴⁺modified Cu_0.99Sr_0.01O ceramics.The ceramics show NTC features,and theirρ₂₅and thermosensitive coefficient(B_25/85)increases monotonously with the rising of Ti⁴⁺content.A proper amount of Ti⁴⁺as dopant can distinctively improve the ageing stabililty.The resistance drift was decrease from17.53%to 1.99%after an ageing process of 250 h under 150°C.（3）Al³⁺,Sr²⁺,B³⁺co-doped CuO(Cu_1-x-y-zSr_xAl_yB_zO)ceramics were synthesized.Their influence on their phase components,microstrcutures and electrical properties was studied.The co-doping of Sr²⁺and Al³⁺can effectively manipulate the electric features of CuO-based ceramics,while the further introduction of B³⁺can further increase theρ₂₅and B_25/85.In Cu_1-x-y-zSr_xAl_yB_zO system,ρ₂₅varies in range of 106.62Ω·cm-4.25MΩ·cm,while B_25/85ranges from 2397 K-5703 K.Electrochemical impedance spectrum（EIS）test of Cu_0.9325Sr_0.01Al_0.03B_0.0275O ceramic revealed that doping of B³⁺increased the resistance of grain effect and grain boundary effect.Both band-conduction mode and hopping-conduction mode are responsible for the grain part within the ceramics,and these two modes,together with energy barrier hopping mechanism,contribute to the NTC character of the whole material.