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1.
Effects of synthesis route on the structural,magnetic and magnetocaloric properties of Pr0.8K0.2MnO3
《Ceramics International》2017,43(2):1853-1861
Pr0.8K0.2MnO3 ceramics are prepared by solid-state reaction and Pechini sol–gel method. The influence of the powder synthesis method on the structural, morphological, magnetic and magnetocaloric properties of the samples are investigated. The X-ray diffraction pattern shows reflections typical of the perovskite structure with orthorhombic symmetry. The experimental results reveal that both samples undergo a second-order phase transition. The maximum magnetic entropy changes, deduced from the M–µ0H measurements, are 3.77 and 7.23 J/kg K under the magnetic field change of 5 T for Pr0.8K0.2MnO3 synthesized by using solid-state reaction and sol–gel methods respectively. The field dependence of magnetic entropy change is analyzed showing the power law dependence, ΔS(T,µ0H)=a(T)(μ0H)n(T,H) at the Curie temperature. Using the scaling laws of ∆S, the experimental ∆S collapse onto a universal curve for both ceramics. These results suggest that the physical properties of our samples are strongly depended on synthesis techniques. It is found that Pechini sol–gel method is more efficient and stable to obtain ceramic materials with good magnetic properties. Consequently, a substantial increase of the ferromagnetic to paramagnetic transition temperature and an enhancement of magnetocaloric properties are observed in the sol-gel made sample making it more suitable for magnetic refrigeration applications. 相似文献
2.
《Ceramics International》2022,48(10):13589-13597
We have systematically investigated the magnetic and magnetocaloric effect (MCE) of REMnO3 (RE = Dy, Eu) manganites sintered by solid-state reaction method. The Neel temperature (TN), the maximum magnetic entropy change (-ΔSmmax) and the relative cooling power (RCP) of the sample were obtained by measuring the magnetization and heat capacity. Under the magnetic field change of 50 kOe, large -ΔSmmax of 8.93J/kg K and 9.31J/kg K are achieved around the TN of 14 K and 50 K for DyMnO3 and EuMnO3, respectively. It is proved by the slope of the Arrott plot and the universal phenomenological curve that the sample undergoes second order phase transition. The critical behavior of antiferromagnetic to paramagnetic phase transition is studied by modifying Arrott plot, which shows that the spin order of the sample decreases at the phase transition temperature and tends to change into shortrange order. The large magnetic entropy change calculated by Landau theory and experimental data indicates that the sample has a large magnetocaloric effect and has potential application in low temperature magnetic refrigeration materials. 相似文献
3.
《Ceramics International》2021,47(18):25304-25313
In this work, the manganite's magnetocaloric properties are studied by changing their chemical composition for a group La0.8-xSmxSr0.2MnO3 (x = 0.0, 0.05, 0.10, and 0.15) ceramic synthesized by the solid-state reaction method. According to the X-ray powder diffraction (XRD) analysis, no sign of a secondary phase is detected. It is found that the prepared samples are formed in the rhombohedral crystal structure with an R-3c space group. There is a decreasing trend in the unit cell volume, which indicates the gradual replacement of Sm in La sites. The results obtained from the energy-dispersive X-ray (EDAX) spectroscopy test indicated that the ratio of elements in the compounds is close to their nominal values. Based on the M measurements (upon the change of temperature) of the as-prepared specimens, an FM transition is observed. The transition temperature decreases upon the increase of the x value. The measured magnetic entropies of all the La0.8-xSmxSr0.2MnO3 samples are an illustration of a magnetocaloric impact on these compounds. This observation introduces La0.8-xSmxSr0.2MnO3 as a potential candidate for applications related to magnetic refrigeration. 相似文献
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5.
Lei Su Xiang-Qun Zhang Qiao-Yan Dong Hai-Tao Yang Shi-Hui Li Zhao-Hua Cheng 《Ceramics International》2021,47(13):18286-18294
The influence of Mn doping on structure, magnetic behaviors and magnetocaloric effect in TmFeO3 polycrystalline ceramics has been explored. X-ray powder diffraction proves that TmFe1-xMnxO3 (x ≤ 0.3) ceramics maintain an orthorhombic structure, and the space group is Pbnm. Compared with the original TmFeO3 sample, structural parameters change slightly and magnetic properties are effectively tuned with the gradual substitution of Mn at Fe site. The spin reorientation temperature region shifts from 90.3 to 73.2 K for TmFeO3 to 180.0–156.0 K for TmFe0.7Mn0.3O3. Besides, for TmFe1-xMnxO3 (x ≤ 0.3), the maximum magnetic entropy changes dependent on the Mn composition are 6.29 J/kg K, 6.56 J/kg K, 6.79 J/kg K and 7.22 J/kg K for 0–70 kOe, respectively. The refrigeration capacities are 159.3 J/kg, 168.9 J/kg, 176.7 J/kg and 184.4 J/kg, respectively. For a better assessing the magnetocaloric performance of TmFe1-xMnxO3 (x ≤ 0.3), we have calculated the temperature average entropy change, refrigerant capacity and normalized refrigerant capacity, and their values become larger with increasing Mn doping. Our experimental results can provide valuable references for the application and development of RFeO3 (R = rare earth) as multifunctional materials. 相似文献
6.
Komal Kanwar Indrani Coondoo M. Anas Vivek K. Malik Pradip Kumar Sandeep Kumar Pawan K. Kulriya S.D. Kaushik Neeraj Panwar 《Ceramics International》2021,47(6):7386-7397
In the present study, the physical properties including structural, optical and magnetic of HoCr1-xMnxO3 (x = 0, 0.15) have been thoroughly investigated and compared. A detailed structural analysis of the compounds provided a way to correlate the optical and magnetic properties with the change in Cr-site ionic radius, tilt angles and distortion in CrO6 octahedra due to Mn substitution. Further, the shift in the Raman phonon modes was associated with the increased structural distortion owing to Mn substitution in HoCrO3 compound. The variation in the Urbach energy values, measured from the diffuse reflectance spectroscopy, was found to be closely related to the octahedral distortion. The optical band gap reduced from 3.22 eV to 2.01 eV after Mn substitution. Other optical parameters such as skin depth, refractive index, extinction coefficient and optical conductivity were also perceived to vary noticeably in the substituted compound. The overall structural distortion with Mn substitution resulted in the decrease of antiferromagnetic transition temperature of the pristine compound. The strong magnetic entropy change was observed at low temperatures in pure HoCrO3 compound and its value was enhanced on Mn substitution. Therefore, the present work provides a convenient method to tune the multifunctional properties of HoCrO3 compound, which has practical applications such as photocatalyst and low-temperature magnetic refrigerant. 相似文献
7.
Effects of temperature and electric field on upconversion luminescence in Er3+‐Yb3+ codoped Ba0.8Sr0.2TiO3 ferroelectric ceramics
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Qiu Sun Weihua Wang Yunxing Pan Zhikai Liu Xiangqun Chen Mao Ye 《Journal of the American Ceramic Society》2017,100(10):4661-4669
Optical and electrical properties of 1%Er3+ and different Yb3+ content (1ExY) codoped Ba0.8Sr0.2TiO3 (BST) ferroelectric ceramics fabricated by the solid‐phase reaction were investigated. Under 980 nm pump condition, two green emission bands at 525 and 549 nm wavelength corresponding to, 2H11/2→4I15/2 and 2S3/2→4I15/2 transitions, and two red emission bands at 655 and 668 nm wavelength attributed to 4F9/2→4I15/2 transition are observed. The temperature‐sensing behaviors, calculated by the intensity ratio I525/I549 suggested that, the maximum sensitivity of the green emission of the 1E8Y‐BST ceramics is 1.07×10?2 K‐1 at 293 K. Furthermore, the maximum sensitivity of 1E6Y‐BST and 1E11Y‐BST ceramics were obtained around the Curie temperature. The fluorescence lifetime of 1E8Y‐BST ceramics for 2H11/2 level and 2S3/2 level shortened with the increase in the temperatures. Moreover, the upconversion (UC) luminescence intensity of 1E8Y‐BST decreased with the increase in the external electric field and had a mutation at the coercive electric field (Ec) of about 1.24 kV/cm, which revealed that the electric field had influence on the UC luminescence. 相似文献
8.
《Ceramics International》2023,49(8):11903-11911
In this study, we aim to examine the critical behavior and magnetocaloric effect of RCrO3 (R = Gd, Dy) polycrystal synthesized by solid-state sintering. As per the heat capacity fitting curves, GdCrO3 and DyCrO3 fit the 3D-XY and 3D-Ising models, respectively. The analysis of heat capacity curves, field cooling (FC), and zero-field cooling (ZFC) curves reveals two magnetic phase transitions in the samples, with TNCr = 174 K, TNGd = 3.7 K and TNCr = 152 K, TNDy = 3.5 K for GdCrO3 and DyCrO3, respectively. Under a 50 kOe magnetic field, the maximum magnetic entropy change (−ΔSmmax) and relative cooling efficiency (RCP) of the sample are 39.9 J/kg K, 373.4 J/kg and 15.9 J/kg K, 276 J/kg for the two samples, respectively. We believe that the significant magnetocaloric effect of GdCrO3 is associated with its critical behavior. This provides an additional reference for the origin of the large magnetocaloric effect of materials. 相似文献
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10.
《Ceramics International》2020,46(7):9129-9135
This work presents the effects of sintering temperature ranging from 1200 °C to 1300 °C at intervals of 20 °C on the crystal structure, ferroelectric properties, and electrocaloric effect (ECE) of Pb0.8Ba0.2ZrO3. Samples sintered at 1240 °C, 1260 °C, and 1280 °C have large remanent polarization and small coercive field. Meanwhile, samples sintered at 1260 °C, 1280 °C, and 1300 °C possess large breakdown field strength. Samples sintered at 1260 °C for 4 h exhibit the optimal ferroelectric properties. Antiferroelectricity-ferroelectricity (AFE-FE) phase transition occurs at room temperature T1 (279 K). Directly examining ECE at this temperature is meaningful, and the temperature change is 0.068 K at approximately 60 °C and 30 kV/cm. Results laid the foundation for studying the performance of ferroelectric and ECE within this phase-transition temperature range and provide a reference for new solid-state refrigeration technology. 相似文献
11.
《Ceramics International》2022,48(7):9239-9247
High entropy perovskites LnCr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 ceramics were produced by solid-state reactions from oxides. The B-site chemical composition was fixed (Cr0.2Mn0.2Fe0.2Co0.2Ni0.2) and A-site composition was varied by the rare-earth ions (Ln = Sm3+, Eu3+ and Gd3+). The entropy of B-sublattice mixing was 1.609R J/(mol*K). The dependences of the lattice parameters, microstructure features, and electrical properties were discussed as function of the A-site rare-earth ions. The correlation of the lattice parameters with the nature of the A-site rare earth ions was demonstrated. Impact of the rare-earth ions in A-site on microstructural parameters was observed. Charge conduction mechanisms were discussed in details for a wide range of temperatures. 相似文献
12.
《Ceramics International》2023,49(6):9412-9418
The properties and hence the applications of negative temperature coefficient (NTC) oxides, NixMn3-xO4, strongly depend on the Ni:Mn ratio, valence states, defects and cation distribution in the spinel structure. Here, the accuracy of determination of nickel and manganese cations distribution in the spinel structure of Ni0.66Mn2.34O4 oxide, has been improved by taking into account the presence of tetrahedral vacancies. Additionally, the structural stability of cubic Ni0.66Mn2.34O4 was investigated as a function of pressure up to 9.5 GPa using synchrotron radiation angle-dispersive X-ray powder diffraction and a diamond anvil cell. The bulk modulus and its first derivative were determined by fitting the Birch-Murnaghan equation of state (EoS) model to the experimental pressure-volume data. Rietveld refinement of the X-ray powder diffraction data reveals that the cubic spinel structure is stable upon compression to 9.5 GPa. The XRD data yielded a bulk modulus of K0 = 126(7) GPa, with a pressure derivative K′ = 12(2). The obtained data were discussed in terms of defects in the cationic sublattice and compared with the elastic parameters of NiMn2O4. 相似文献
13.
We apply first-principles calculations to study the influence of pressure on the structure, elastic modulus, hardness, brittle-or-ductile behavior and melting point of NbSi2. Four NbSi2 phases: C40, C11b, C54 and C49 are considered based on the structural feature. The results show that the calculated formation enthalpy of the four NbSi2 phases is negative within the pressure range of 0–60 GPa, indicating that they are thermodynamically stable in whole pressure. In particular, the calculated formation enthalpy of the C54 NbSi2 is smaller than the other NbSi2 phases, indicating that the C54 NbSi2 is more thermodynamically stable than the other NbSi2 phases. The calculated elastic modulus and Vickers hardness of NbSi2 increase with increasing pressure. Note that the pressure results in brittle-to-ductile transition of the C40 NbSi2, C11b NbSi2 and C54 NbSi2 between 30 GPa and 60 GPa. Naturally, the increasing of mechanical properties is that the pressure enhances the electronic hybridization between Nb and Si, which is demonstrated by the chemical bonding such as Nb–Si bond and Si–Si bond. 相似文献
14.
《Ceramics International》2023,49(4):6068-6076
Ferroelectric ceramics have good piezoelectric and ferroelectric properties and can be used for energy storage equipment and actuators. Nevertheless, current research on dielectric capacitors has only focused on the energy storage density, but ignored efficiency. Moreover, conventional piezoelectric materials have a large strain hysteresis. In this work, (Al0.5Nb0.5)4+ (AN) complex ions doped 0.7Bi0.5Na0.5TiO3-0.3Ba0.3Sr0.7TiO3 (BNBST) ceramics were prepared. Doping AN destroyed the long-range ordered ferroelectric domains and generated polar nano regions, resulting in a gradual thinning and inclination of polarization hysteresis loops and an increase in relaxor degree. For BNBST-3AN ceramics, a Wrec of 1.52 J/cm3 and a η of 92.1% were achieved at 150 kV/cm. Meanwhile, BNBST-3AN ceramics had good energy storage temperature stability and cycling performance. The AN doping reduced the strain hysteresis in BNBST ceramics. BNBST-2AN ceramics exhibited a longitudinal electrostrictive coefficient Q33 ~ 0.0292 m4/C2 and a field-induced strain of 0.25% with low strain hysteresis (6.67%). Furthermore, BNBST-4AN ceramics had superior dielectric temperature stability from 24 to 270 °C. All results show that BNBST-100xAN ceramics have great promise for energy storage devices and actuators. 相似文献
15.
《Ceramics International》2022,48(14):20010-20019
Mn2+/Al3+-, Eu2+/Mn2+-, and Eu2+/Mn2+/Al3+-doped high silica glasses were prepared to investigate their photoluminescence and radioluminescence properties. Particularly, the effect of Al3+ on the energy transfer from Eu2+ to Mn2+ and the regulation law of Mn2+ luminescence properties in Mn2+/Al3+- and Eu2+/Mn2+/Al3+-doped glasses were investigated. A strategy to improve the radioluminescence intensity of glasses was developed, and the radioluminescence intensity formula was improved. The dispersion caused by Al3+ improves the luminous intensity of Mn2+ and lowers the efficiency of the Eu2+→Mn2+ energy transfer in high silica glass. Al3+ can significantly broaden the excitation spectrum of Mn2+ by affecting the coordination number of Mn2+ and changing the field intensity around Mn2+ ions. Notably, the developed glass can potentially be applied in laser and LED lights. In addition, nonbridging oxygens (NBOs) are considered to be the main factor leading to the low efficiency of glass radioluminescence. Al3+ is able to reduce the relative amount of NBOs by forming [AlO4/2]?1 tetrahedra, thereby improving the radioluminescence intensity effectively. 相似文献
16.
《Ceramics International》2016,42(4):4734-4738
Hysteresis loop is very important for the application of ferroelectric ceramics. Here the competition effects of grain boundary and aging on the hysteresis loop behavior of Mn doped (Ba0.8Sr0.2)TiO3 ceramics were studied. The results show that a double hysteresis loop appears after aging. Nevertheless, Pmax of small grained ceramics decreased clearly but Pr decreased little with aging time increases; large grained ceramics have the opposite result. Such difference is caused by the competition effect on their domain switching behavior, from aging-induced time-dependent internal defect field and grain boundary generated time-independent back field. This study may provide help on the control of hysteresis loop by grain size and aging. 相似文献
17.
We investigated the hydration and swelling properties of poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide)-poly(N,N-diethylacrylamide) derived microgels by Fourier transform infrared- (FTIR-) spectroscopy in a wide region of the temperature-pressure plane. These systems are known to show a swollen-to-collapsed-transition upon temperature elevation. Our data reveal that pressure favours the swollen, hydrated state over the collapsed state in all systems investigated. A detailed analysis of the fractions of the respective IR sensitive amide-I′-subbands allowed the calculation of ΔGo and ΔVo for the pressure-induced swelling process as well as evaluation of various intra- and intermolecular hydrogen bonding connectivities in the different systems. In fact, considerable differences exist between different polymer or microgel types with regards to their hydrogen bonding pattern as a function of temperature and pressure, and the microgels may even exhibit a biphasic swelling behavior. Notably, the thermodynamic parameters derived reveal to be in the same order of magnitude as measured for the pressure and cold denaturation of proteins. 相似文献
18.
采用溶胶-凝胶方法制备了系列样品La0.75Sr0.25-xKxMnO3(x=0.00,0.05,0.07,0.10).对系列样品进行了相结构、磁性和电输运性质的研究.XRD数据表明:系列样品具有完整的钙钛矿锰氧化物结构.通过对磁性和电阻率的研究发现:与双交换作用相比,A位离子的无序度2对样品的磁性和电输运的影响起主要作用.随掺杂量的增加,磁电阻的峰值逐渐增大;峰值温度逐渐下降,更接近室温.在210~280 K的温区内,磁电阻基本保持稳定.这些结果都有利于磁电阻的实际应用. 相似文献
19.
Yong Li Jie Yuan Dawei Wang Deqing Zhang Haibo Jin Maosheng Cao 《Journal of the American Ceramic Society》2013,96(11):3440-3447
Nb and Mn were doped, respectively, to 0.8Pb(Sn0.46Ti0.54)O3–0.2Pb(Mg1/3Nb2/3)O3 (PST–PMN) to improve electrical properties for meeting the requirement in various fields. The additions of Nb and Mn influence in a pronounced way the structure, and improve the densities of the ceramics. Nb‐doped PST–PMN increased the piezoelectric coefficient d33, planar electromechanical coupling kp, and relative dielectric constant ε, indicating “soft” piezoelectric behavior. Mn doping played a “hard” part, which significantly enhanced the mechanical quality factor Qm without deteriorating other piezoelectric properties. The most excellent properties of Nb‐doped PST–PMN were obtained with doping amount of 0.75 mol%, specifically d33, kp, being on the order of 455 pC/N, 57.5% and 3560, respectively. The addition of 0.75 mol% Mn for PST–PMN presented the optimum electrical properties, with Qm of 554, d33 of 430 pC/N, kp of 57.0%, ε of 2770. It was proposed that the addition of Nb, Mn generated different defect dipoles involved in the domain walls motion and intrinsic piezoelectric responses, leading to different effects on electrical properties. 相似文献
20.
Hong Xu Shangkun Zhou Yiming Zhu Weigang Xu Xiaohe Xiong Houzhang Tan 《中国化学工程学报》2019,27(8):1956-1964
Aiming at the high temperature corrosion in a coal-fired boiler, the effect of H2S and SO2 on the corrosion of 12Cr1MoV under the water wall condition has been investigated by experiments. The results indicate that H2S can promote the corrosion significantly, and the coarse porous oxide film formed cannot stop the progress of corrosion. While SO2 presents little effect on the corrosion. The main composition of the surface of 12Cr1MoV corrosion products is Fe2O3. With H2S in the atmosphere, the corrosion gradually develops into deeper layers by forming FeS, FeO and Fe2O3 alternately. The corrosion rate is doubled for every 50 °C increase in temperature at 400–500 °C. 相似文献