Electrical properties and stability of low temperature annealed (Zn,Cu) co-doped (Ni,Mn)₃O₄ spinel thin films

Abstract

Toward the development of infrared (IR) detectors, nickel-manganite-based thin films were initially prepared from (Ni 0.2 Mn 2.8-x Cu x )Cl 2 (0.010 ≤ x ≤ 0.040) solutions using the liquid flow deposition (LFD) method. The influence of Cu on the negative temperature coefficient of resistance (NTCR) characteristic of the films annealed at 400°C was investigated. It was found that the incorporation of Cu can effectively enhance electrical conductivity; however, it degrades both the thermal sensitivity and stability of the nickel-manganite films. The investigation was extended by further modifying the composition with Zn. The results revealed that by co-doping Cu with a proper amount of Zn the temperature coefficient of resistance (TCR) could be tailored, while a relatively low resistivity (ρ) of the final products was retained. Specially, when 0.01 mol Zn was added to a precursor solution containing 0.025 mol Cu, the resulting specimen possessed a TCR = 2.82% K -1 and a ρ = 820 Ω (measured at RT). More importantly, compared to Zn-free films, the (Zn,Cu) co-doped compositions showed much improved electrical stability, with an aging coefficient (ΔR/R) as low as 4.6%, after aging at 150° C in air for 500 h. The results suggest that the (Zn,Cu) co-doped (Ni,Mn) 3 O 4 thin films have a promising application in IR detectors.

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

“…Adding Zn to the system can reduce the aging value to 2.6%, which, however, increases the resistivity above 1049 Ω•cm. Similar phenomena occur in Zn x Cu 0.2 Ni 0.66 Mn 2.14−x O 4 [19], Ni 0.6 Cu 0.5 Zn x Mn 1.9−x O 4 [20], Ni 0.2 Mn 2.8−x−y Cu x Zn y O 4 [21], and Cu 0.25 Zn 1.0 Ni 0.5 Mn 1.25 O 4 [26]. It can be seen that the preparation of single-phase spinel structure NTC ceramics with low resistivity and high stability still faces challenges.…”

“…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.…”

“…This may be due to combined effect of the twins and dual phases, which will be discussed below. Cu-containing NTC ceramics usually exhibit low resistivity but poor stability [18][19][20][21][24][25][26]43,59,60], as summarized in Table 2. In contrast, the Co 0.98 Cu x Mn 2.02−x O 4 ceramics with multiphase and twin structures show both low resistivity and excellent stability.…”

Nano–Crystalline Mn–Ni–Co–O Thermistor Powder Prepared by Co–Precipitation Method

“…Table 3 also shows an average ∆R/R value of 1.43% after the ceramics were aged for 500 h, demonstrating extremely high stability. It has been reported that aging behavior is primarily caused by the oxidation reactions during metallization [39,40]. Therefore, the little change in resistance here can be supported by the dense and fine-grained microstructure shown in Figure 7 (AGS~1.82 µm), which suppresses oxygen adsorption, leading to more stable spinel lattices [41].…”