Effect of co‑precipitation method on characteristic values of yYCrxMn1-xO3-（1-y） Y2O3 system

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Effect of co‑precipitation method on characteristic values of yYCrxMn1-xO3-（1-y） Y2O3 system

Journal Title: China Powder Science and Technology - Year 2025, Vol 31, Issue 2

Abstract

[Objective] Negative temperature coefficient （NTC） thermistors are widely used in fields such as automotive electronics， household appliances， aerospace， and medical equipment due to their ability to measure temperature， provide temperature compensation， and suppress inrush current. To enhance the resistivity （ρ） and reduce the thermal sensitivity constant （B） of ceramic NTCs， this study investigates the effect of the co-precipitation method on the characteristic values of the yYCrxMn1-xO3-（1-y）Y2O3 system by adjusting the x and y ratios. [Methods] Initially， during the preparation stage of the solid-phase method， eight different ratios of x and y were precisely selected to prepare rare-earth perovskite negative temperature coefficient thermistor （NTC） samples according to the yYCrₓMn₁₋ₓO₃-（1-y）Y₂O₃ system. The raw materials Y₂O₃， Cr₂O₃， and MnCO₃ were accurately weighed according to each ratio. After steps such as grinding and mixing， they were pressed into shape and then sintered in a high-temperature furnace under specific temperature and time conditions. Subsequently， the crystal structure and phase composition of the samples were analyzed using X⁃ray diffraction （XRD） technology. Meanwhile， electrical performance analysis was carried out to comprehensively evaluate parameters such as the direct current resistivity， thermistor constant B₂₅/₈₅， and activation energy Eₐ of the samples. After careful comparison， the optimal ratio （x=0.3， y=0.6） was finally selected.On this basis， the chemical co-precipitation method was adopted. YCl₃·6H₂O， CrCl₃·6H₂O， and MnCl₂·4H₂O were calculated， weighed， and batched according to a total mass of 100 g. They were dissolved in 5 mL of deionized water and continuously stirred. In a reverse addition manner， the solution was added to ammonia water and continuously stirred， keeping the pH of the solution at around 10. After stirring for 2 h， the solution was allowed to stand for precipitation. The supernatant was poured off， and the precipitate was washed with deionized water until neutral and then rinsed with absolute ethanol. After drying， it was pre-sintered at 800 ℃ for 2 h. According to the masses of YCr₀.₃Mn₀.₇O₃ and Y₂O₃ corresponding to different y values， they were weighed， ground evenly， pressed into small round pieces of specific specifications， and sintered at 1 250 ℃ for 4 h to obtain negative temperature coefficient thermistor ceramics. Through the study of the properties of these ceramics， the influence of the co-precipitation method on the product performance was deeply explored. [Results and Discussion] In the yYCr0.3Mn0.7O3-（1-y）Y2O3 system prepared by the co-precipitation method， when y≥0.6， the thermal sensitivity constant B25/85 was ≥2 180 K， and the activation energy Ea was ≥0.19 eV. Conclusion By increasing the mass fraction of Mn4+ and decreasing the mass fraction of Y2O3， the yYCr0.3Mn0.7O3-（1-y）Y2O3 phase content can be increased， thereby reducing the material’s resistivity. This leads to improved sensitivity of the resistive value to temperature changes， reflected by an increase in the thermal sensitivity constant （B value）.

Authors and Affiliations

Dian WANG, Guangyuan XIE, Juntao LYU, Wanwan LI

Keywords

EP ID EP760556
DOI 10.13732/j.issn.1008-5548.2025.02.009
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