Novel Method for NTC Thermistor Production by Aerosol Co-Deposition and Combined Sintering

Abstract

A novel three-stage process to produce NTCR sensors is presented. In this process, an uncalcined powder mixture of NiO and Mn2O3 was deposited onto an alumina substrate via aerosol co-deposition (AcD). Then, an electrode structure was screen-printed onto the surface and the composite film was sintered in a multifunctional temperature treatment. Thereby, the sintering of the electrode, the formation of the NiMn2O4 spinel and the removal of film strains took place simultaneously. This enabled a significant reduction in energy demand and workload. The manufactured sensors, both as first prototypes, as well as miniaturized chip components, were characterized by a single-phase cubic NiMn2O4 spinel structure, mechanical stability and electrical properties that were similar to those of classical NiMn2O4 bulk ceramics or tempered aerosol deposited (AD) NiMn2O4 films. Particularly noteworthy was the high reproducibility and low variation of the NTCR parameters, such as the specific resistivity at 25 °C ρ25, the electrical resistance at 25 °C R25 and the thermistor constant B. The NTCR parameters were as aging-stable as for NiMn2O4 bulk ceramics or tempered NiMn2O4 AD-films and could even be further improved by thermal post-treatment.

Electrospun Nickel Manganite (NiMn2O4) Nanocrystalline Fibers for Humidity and Temperature Sensing

“…As noted before for NiMn 2 O 4 [ 18 , 19 , 29 ] as an NTC thermistor material, the measured DC resistance decreased with an increase in temperature (20–50 °C), following an exponential Arrhenius dependence [ 18 ], as shown in Figure 5 and the equation where R ∞ is the reference resistance of the thermistor, representing resistance at an infinite temperature when 1/ T = 0, T is the temperature expressed in K, and B is the material constant (or B-value) of the thermistor.…”

“…Nickel manganite is a well-known NTC thermistor oxide material, low-cost, non-toxic and abundant [ 18 ], with a cubic spinel structure and a small polaron hopping conduction mechanism between manganese cations (Mn 3+ and Mn 4+ ) [ 19 , 20 ]. It has extensively been investigated as an NTC thermistor in bulk, thick or thin film form [ 19 , 21 , 22 , 23 ].…”

“…Nickel manganite is a well-known NTC thermistor oxide material, low-cost, non-toxic and abundant [ 18 ], with a cubic spinel structure and a small polaron hopping conduction mechanism between manganese cations (Mn 3+ and Mn 4+ ) [ 19 , 20 ]. It has extensively been investigated as an NTC thermistor in bulk, thick or thin film form [ 19 , 21 , 22 , 23 ]. Recently, nickel manganite has been the subject of much research for energy storage as a supercapacitor, [ 24 , 25 ] in photocatalysis [ 26 ], or as anode material for lithium-ion batteries [ 27 ].…”

Powder aerosol deposition method — novel applications in the field of sensing and energy technology

“…38 The authors also developed a novel process, in which the approach of powder aerosol co-deposition with subsequent in situ calcination is combined with the sintering of screen-printed electrodes. 39 The advantage of this approach is only one single temperature treatment at 850 ○ C is required to produce mechanically stable NTCR sensors with the same 25 À and B-values as classically sintered bulk ceramics. Due to the possibility to produce fully dense and mechanically stable films with typical NTCR characteristics by PAD or by AcD with subsequent in situ calcination, both approaches are very interesting for a possible utilization in NTC thermistor applications.…”

“…In addition, more and more powder mixtures are being used. 6,7,[36][37][38][39] Due to the large variety of ceramic raw powders, powder mixtures and substrate materials, powder aerosol deposited films show diverse properties and thus are used or suggested for many applications these days. In this overview, different applications of powder aerosol deposited film are presented with special focus on the field of sensing and energy technology.…”