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

WANG Dian; XIE Guangyuan; LYU Juntao; LI Wanwan

doi:10.13732/j.issn.1008-5548.2025.02.009

Abstract：Objective Negative temperature coefficient(NTC)thermistors are widely used in fields such as automotive electronics,house-hold appliances,aerospace,and medical equipment due to their ability to measure temperature,provide temperature compensa-tion,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-x O3-(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 tem-perature 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/s5,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 neu-tral and then rinsed with absolute ethanol.After drying,it was pre-sintered at 800 ℃ for 2 h.According to the masses of YCr0.3 Mn0.7O3 and Y2O3 corresponding to different y values,they were weighed,ground evenly,pressed into small round pieces of spe-cific specifications,and sintered at 1 2500℃ 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 yYCr03Mn0.7O3-(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).