Effect of Ca and Ag doping on the functional properties of BiFeO 3 nanocrystalline powders and films
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Effect of Ca and Ag doping on the functional properties of BiFeO3 nanocrystalline powders and films Gina Montes Albino1, Oscar Perales-Pérez3, Boris Renteria-Beleño3 and Yarilyn Cedeño-Mattei3 1
Department of Mechanical Engineering, University of Puerto Rico at Mayagüez P.O. Box 9045, Mayagüez, PR, 00681-9045 USA. 2 Department of Physics, University of Puerto Rico at Mayagüez, Mayagüez, PR, 00980, USA. 3 Department of Engineering Science and Materials, University of Puerto Rico at Mayagüez, Mayagüez, PR, 00680-9044, USA. ABSTRACT The present work addresses the systematic evaluation of the influence of the incorporation of dopant species (Ca+2, Ag+1) on the structural and functional properties of bismuth ferrite (BFO) nanocrystalline powders and films. Pure and doped BFO powders and thin films were synthesized by a modified sol-gel method. The concentration of the doping species varied from 0 up to 7 at %. The development of the host BFO structure was confirmed by XRD analyses of samples annealed at 700°C for one hour in air and nitrogen atmosphere. Thicknesses of films varied between 80 and 200 nm, depending on the concentration of Ca+2 species. Doped BFO exhibited a magnetic behavior that turned from paramagnetic into ferrimagnetic with the increase of Ca+2 concentrations. INTRODUCTION Proper-primary type BiFeO3 (BFO)-based multiferroics are rhombohedrally distorted acentric structure (space group R3c) that exhibit G-type antiferromagnetic order with a long-periodicity spiral below the Neel temperature of 643 K and ferroelectricity below 1103 K. The ferroelectricity of BiFeO3 is due to Bi3+ 6s2 lone-pair distortions, whereas the residual moment of the canted Fe3+spin structure results in weak ferromagnetism.Recently, perovskite-type transition metal oxides ABO3 are of great interest because of their magnetic, dielectric, and transport properties that emerge from the coupling of spin, charge, and orbital degrees of freedom. A-site substitutions of trivalent (La3+, Nd3+, or Sm3+) 1-6 or divalent (Ba2+, Pb 2+,Sr2+, or Ca2+) 7-10 species for Bi3+and B-sublattice dopings with V5+, Nb5+, Mn4+, Ti4+, or Cr3+ ions, have recently been investigated in order to improve the magnetoelectric coupling11-15. BFO perovskite type, proper and lead-free multiferroic material can find potential and promising applications in the development of multifunctional devices, solar energy devices, ferroelectric random access memory and spintronics. These applications rely on the observed (anti)ferroelectricity, (anti)ferromagnetism, and ferroelasticity behaviors in a single crystalline phase. On this basis, the present work will attempt to find a suitable combination of deposition parameters, via a modified sol-gel approach, for improving multifunctional BFO properties in powders and films. If oxygen vacancies are generated during the material forming stage, structural, magnetic and electric transitions could be tuned and hence, optimized. Therefore, the annealing stage of the precursor solids will be carried out in a close-system in air or ni
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