Atilla COŞKUN, Büşra ZOR

Pr1.4-xLaxSr1.6Mn2O7 (x: 0; 0,4; 0,7; 1,0) Çift Perovskit Manganit Bileşiklerin Yapısal ve Elektriksel Özelliklerinin İncelenmesi

Bu çalışmada sol-jel yöntemi kullanılarak hazırlanan ve 1000 oC’de hava ortamında 24 saat sinterlenen Pr1.4-xLaxSr1.6Mn2O7 (x:0; 0.4; 0.7; 1.0) bileşiklerinin yapısal, morfolojik ve elektriksel özellikleri incelenmiştir. X-ışınları kırınım desenleri (XRD) analizleri sonucunda, bileşiklerin farklı oranlarda I4/mmm uzay grubuna sahip (tetragonal) çift perovskit ve R3 ̅c uzay gurubuna sahip (trigonal) tek perovskit bileşiklerinden meydana geldiğini ortaya koymuştur. Tüm bileşikler içerisinde baskın olan perovskit fazın, tek perovskit faz olduğu ve artan La katkılamasına bağlı olarak bu fazın ağırlık yüzdesinin arttığı yapılan XRD arıtımları sonucunda bulunmuştur. Bileşiklerin atomik kuvvet mikroskobu (AFM) ve enerji dağılımlı x-ışını spektroskopi (EDS) ataçmanına sahip taramalı elektron mikroskobu (SEM) analizlerinden, La iyonlarının Pr iyonları ile yer değiştirmesine bağlı olarak, yüzeydeki tanelerin büyüdüğü ve boşlukların azaldığı bulunmuştur. EDS analizleri sonucunda hedeflenen bileşiklerin stokiyometrilerine uygun bir şekilde başarılı olarak üretildiklerini ortaya koymuştur. Sıcaklığa bağlı olarak değişen elektriksel direnç ölçümlerinden (R-T), yarıiletken davranış gösteren ve La iyonu içermeyen Pr1.4Sr1.6Mn2O7 bileşiğinin direnç davranışının La iyonlarının yapıya girmesi ile değiştiği ve en çok La içeren bileşiğin yaklaşık 165,4 K’de metal-yalıtkan (TIM) faz geçişi gösterdiği bulunmuştur.

Investigation of Structural and Electrical Properties of Pr1.4- xLaxSr1.6Mn2O7 (x: 0; 0.4; 0.7; 1.0) Double Perovskite Manganite Compounds

In this study, the structural, morphological and electrical properties of Pr1.4- xLaxSr1.6Mn2O7 (x:0; 0.4; 0.7; 1.0) compounds prepared using the sol-gel method and sintered for 24 hours in air at 1000 oC were investigated. As a result of X-ray diffraction patterns (XRD) analysis, it was revealed that the compounds were composed of double perovskites with I4/mmm space group (tetragonal) and single perovskite compounds with R3 ̅ c space group (trigonal) in different ratios. It was found as a result of XRD refinements that the dominant perovskite phase among all compounds was the only perovskite phase and the weight percentage of this phase increased due to the increasing La doping. From the scanning electron microscopy (SEM) analyzes of the compounds with atomic force microscopy (AFM) and energy dispersive x-ray spectroscopy (EDS) attachment, it was found that the grains on the surface grew and the voids decreased due to the displacement of La ions with Pr ions. As a result of EDS analysis, it was revealed that the targeted compounds were successfully produced in accordance with their stoichiometry. From the electrical resistance measurements (R-T) that change depending on the temperature, it is seen that the resistive behavior of the Pr1.4Sr1.6Mn2O7 compound, which shows semiconductor behavior and does not contain La ions, changes with the introduction of La ions into the structure, and that the compound containing the most La is a metal- insulator (TIM) at approximately 165.4 K. ) was found to show a phase transition.

PDF

___

[1] A. C. Hudgins and A. S. Pavlovic Jr., “Magnetocaloric Effect in Dysprosium,” J. Appl. Phys, vol. 36, pp. 3628-3630, 1965.
[2] G. V. Brown, “Magnetic Heat Pumping Near Room Temperature,” J. Appl. Phys, vol. 47, pp. 3673-3680, 1976.
[3] T. Hashimoto, T. Numasawa, M. Shino and T. Okada, “Magnetic Refrigeration in the Temperature Range from 10 K to Room Temperature: The Ferromagnetic Refrigerants,” Cryogenics vol. 21, pp. 647-653, 1981.
[4] V. K. Pecharsky and K. A. Gschneidner Jr, “Giant Magnetocaloric Effect in Gd5(Si2Ge2),” Phys. Rev. Lett, vol. 78, pp. 4494-4497, 1997.
[5] V. K. Pecharsky and K. A. Gschneidner Jr, “Phase Relationships and Crystallography in the Pseudobinary System Gd5Si4-Gd5Ge4,” J.Alloys and Compounds, vol. 260, pp. 98-106, 1997.
[6] K. A. Gschneidner Jr. and V. K. Pecharsky, “Magnetocaloric Materials,” Annual Review of Materials Science, vol. 30, pp. 387-429, 2000.
[7] N. T. Hien and N. P. Thuy, “Preparation and Magnetocaloric Effect of La1-xAgxMnO3 (x= 0.10-0.30) Perovskite Compounds,” Physica B, vol. 319, pp. 168-173, 2002.
[8] D. T. Morelli, A. M. Mance, J. V. Mantese and A. L. Micheli, “Magnetocaloric Properties of Doped Lanthanum Manganite Films,” J. Appl. Phys, vol. 79, pp. 373-375, 1996.
[9] Z. B. Guo, Y. W. Du, J. S. Zhu, H. Huang, W. P. Ding and D. Feng, “Large Magnetic Entropy Change in Perovskite-Type Manganese Oxides,” Phys. Rev. Lett, vol. 78, pp. 1142-1145, 1997.
[10] A. O. Ayas, M. Akyol and A. Ekicibil, “Structural and Magnetic Properties with Large Reversible Magnetocaloric Effect in in (La1-xPrx)(0.85)Ag0.15MnO3 (0.0 < x < 0.5) Compounds,” Philosophical Magazine, vol. 96, no. 10, pp. 922-937, 2016.
[11] E. Taşarkuyu, A. E. Irmak, A. Coşkun and S. Aktürk, “Structural, Magnetic and Transport Properties of La0. 70Sr0. 21K0. 09MnO3,” Journal of Alloys and Compounds, vol. 588 pp. 422–427, 2014.
[12] S. Das and T. K. Dey, “Magnetocaloric Effect in Potassium Doped Lanthanum Manganite Perovskites Prepared by a Pyrophoric Method,” J. Phys.: Condens. Matter, vol. 18, pp. 7629-7641, 2006.
[13] A. Gaur and G. D. Varma, “Sintering Temperature Effect on Electrical Transport and Magnetoresistance of Nanophasic La0.7Sr0.3MnO3,” J. Phys.: Condens. Matter, vol. 18, pp. 8837-8846, 2006.
[14] I. Dhiman, A. Das, A. K. Nigam and R. K. Kremer, “Effect of B-Site Doping in (La0.3Pr0.7)0.65 Ca0. 35Mn1− xBxO3 (B= Fe, Cr, Ru and Al) Manganites,” Journal of Magnetism and Magnetic Materials, vol. 334, pp. 21-30, 2013.
[15] A. Maignan, F. Damay, A. Barnabé, C. Martin, M. Hervieu, and B. Raveau, “The Effect of Mn-site Doping on the Magnetotransport Properties of CMR Manganites,” Philosophical Transactions of the Royal Society A, vol. 356, no. 1742, pp. 1635-1659, 1998.
[16] A. Coşkun, E. Taşarkuyu, A. E. Irmak, M. Acet, Y. Samancıoğlu and S. Aktürk, “Magnetic Properties of La0.65Ca0.30Pb0.05Mn0.9B0.1O3 (B= Co, Ni, Cu and Zn),” Journal of Alloys and Compounds, vol. 622, pp. 796-804, 2015.
[17] A. Mishra and S. Bhattacharjee, “Effect of A- or B-site Doping of Perovskite Calcium Manganite on Structure, Resistivity, and Thermoelectric Properties,” Journal of the American Ceramic Society, vol. 100, no. 10, pp. 4945-4953, 2017.
[18] M. H. Ghozza, I. S. Yahia and S. I. El-Dek, “Role of B-site Cation on the Structure, Magnetic and Dielectric Properties of Nanosized La0.7Sr0.3Fe1−xMxO3 (M = Mn; Co and x = 0, 0.5),” Perovskites. Mater. Res. Express, vol. 7, pp. 056104-056128, 2020.
[19] R. Dudric, F. Goga, M. Neumann, S. Mican and R. Tetean, “Magnetic Properties and Magnetocaloric Effect in La 1.4− xCe xCa1.6Mn2O7 Perovskites Synthesized by Sol–Gel Method,” Journal of Materials Science, vol. 47, pp. 3125-3130, 2012.
[20] G. Yu, B. Xu, J. Xiong, X. Liu, L. Liu and S. Yuan, “Effect of Cr Doping in the Bilayer manganite La1.4Sr1.6Mn2O7,” Journal of Magnetism and Magnetic Materials, vol. 323, no. 15, pp. 1925-1928, 2011.
[21] D. Louca, G. H. Kwei and J. F. Mitchell, “Local Lattice Effects in the Layered Manganite La1.4Sr1.6Mn2O7.,” Phys. Rev. Lett, vol. 80, pp. 3811-3814, 1998.
[22] A. H. Wang, G. H. Cao, Y. Liu et al., “Magnetic entropy change of the layered perovskites La2-2xSr1+2xMn2O7,” Journal of Applied Physics, vol. 97, pp. 103906-103909, 2005.