Effect of La₂O₃ Addition on Copper‐Nickel Manganese Thermistors for Low‐Temperature Applications

Abstract

The introduction of La2O3 to Mn0.75Ni1.25CuO4 ceramics was studied on the microstructure and electrical properties. The sintered Mn0.75Ni1.25CuO4‐xLa2O3 (0 ≤ x ≤ 0.3) bodies was typical polycrystalline, with cubic spinel structure of copper manganese oxide, rocksalt structure of nickel copper oxide, along with monoclinic phase of copper oxide and orthorhombic perovskite structure of lanthanum manganese oxide. It is found that La doping reduces the material grain size and changes its morphology from the plate‐like form to a spherical staking‐like form. The shape and size of the grains are strongly influenced by the addition of La to the system. The X‐ray photoelectron spectroscopy analysis corroborates the presence of nonequivalent ions at octahedral sites. The obtained ρ77K, B77K/90K constant and activation energy of the negative temperature coefficient (NTC) Mn0.75Ni1.25CuO4‐xLa2O3 thermistors were in the range of 13.19–30.39 Ω cm, 315–326 K, and 0.0272–0.0281 eV, respectively. This means that the electrical properties can be adjusted to desired values, depending on the La content. Such ceramics could be used as potential candidates for NTC thermistors in a temperature range from 20 K to 90K. So these prepared NTC thermistors were intended to be used under low‐temperature conditions.

Enhanced conductivity and stability of Co 0.98Cu x Mn 2.02− x O 4 ceramics with dual phases and twin structures

“…Various elements, such as Cu, Ni, Fe, Sr, Sn, and Co have been introduced into the Mn 3 O 4 matrix to adjust the Mn 3+ /Mn 4+ couple concentration and carrier jump distance [12][13][14][15][16]. Among the materials mentioned above, only Cu-containing NTC ceramics have resistivity less than 100 Ω•cm [6,[17][18][19][20][21]. However, under thermal constraints, the Cu-containing NTC ceramics show poor electrical stability, which makes them difficult for long-term applications.…”

Structure and Properties of Barium and Strontium Cobaltites Synthesized in a Solar Furnace

“…Recently, more and more attention has been paid to barium cobaltite oxide due to its semiconductor characteristics [6][7][8][9]. Materials based on BaCoO 3-δ doped with some other elements have low resistivity at low temperatures and can be used as thermistors.…”

Electrical properties of Y/Mg modified NiO simple oxides for negative temperature coefficient thermistors

“…The preparation methods, sintering atmosphere and sintering process affect obviously the valence states and distribution of cations, and therefore have a strong effect on the electrical properties. In order to improve the electrical properties of the spinel manganates thermistors, element doping was carried out …”