Intrinsic resistivity of sintered Nickel Manganite vs. powder activation time and density

Abstract

In this work the DC resistivity of sintered nickel manganite NiMn2O4 (NTC thermistor material) was studied as a function of additional powder activation time in a planetary ball mill (0, 5, 15, 30, 45 and 60 min). The activated powders and non-activated powder were sintered at different temperatures (900, 1050 and 12000C) for an hour. Structural changes were analyzed using XRD. Sample density, porosity and DC resistivity were measured on the same sintered samples. Correlations between sample density, porosity, and intrinsic DC resistivity vs. additional powder activation time and the sintering temperature were made. It was noticed that the resistivity falls with the increase of sample density (or increase of the sintering temperature)

Thermal Treatment of Aerosol Deposited NiMn2O4 NTC Thermistors for Improved Aging Stability

“…Together with a dense, nanocrystalline film structure with crystallite sizes in the AD-typical range of 20 nm [19,40,41,43] and an excellent adhesion to both the substrate and the electrode, a successful aerosol deposition according to the RTIC mechanism [22] can be assumed. The achieved NTCR characteristics, B constant with 4250 K and specific resistance at 25 °C ρ 25 with about 65 Ω·m are independent of the electrode material and well above the typical values of bulk ceramics (3500 K–3900 K and 20 Ω·m–30 Ω·m [4,45,46,47,48]). This can be attributed to several factors: used powder, nano-grained film structure and production-related film strains.…”

Highly Dense and Nanograined NiMn2O4 Negative Temperature coefficient Thermistor Thick Films Fabricated by Aerosol‐Deposition

“…A similar tendency of the annealing effect has been reported in electron beam deposited NTC films and sintered bodies, 9,10,18 but more detailed investigation should be conducted to clarify the annealing effect of AD‐NTC films. Although the B constant was decreased by the annealing process, it was maintained over 3500 K, which is much higher than that of other high temperature sintered bulk ceramics (3500–3000 K) 19 or screen‐printed, undoped, NiMn 2 O 4 thick films (2382 K), 6 but similar to the e‐beam evaporated one (4000–3000 K) 10 …”

Study of NiFe2O4and ZnFe2O4Spinel Ferrites Prepared by Soft Mechanochemical Synthesis

“…The activation energy for the thermally activated hopping process was obtained by fitting the DC conductivity data with the Arrhenius relation [18] …”