Effect of La doping on structural, magnetic, and optical properties of KBiFe 2 O 5

In this work, we report the effect of doping with lanthanum ions on structural, magnetic and optical properties of potassium bismuth ferrite KBiFe 2 O 5 (KBFO). KBi 1−x La x Fe 2 O 5 (0 ≤ x ≤ 0.15) samples were synthesized using citrate assisted sol–gel technique. X-ray diffraction analysis revealed the crystal structure of KBi 1−x La x Fe 2 O 5 (0 ≤ x ≤ 0.15) to be monoclinic, without any significant change in the unit cell parameters. Magnetic properties of the compound enhanced with La doping. Maximum magnetization for an applied magnetic field of 15 kOe for the KBi 1−x La x Fe 2 O 5 samples were 0.12 emu/g, 0.28 emu/g, 0.71 emu/g and 1.00 emu/g for x = 0, 0.05, 0.10 and 0.15 respectively. Maximum magnetization increased with lanthanum doping. However, coercivity of the samples reduced drastically when doped with lanthanum (from H c = 212.90 Oe for x = 0 to H c = 18.43 Oe for x = 0.15). Along with magnetic properties, optical properties were also studied using diffuse reflectance spectroscopy and photoluminescence spectroscopy. Narrowing of the optical band gap was observed in La doped samples. Photoluminescence spectra of all the samples at excitation wavelength of 450 nm showed emission peaks at 552 nm and 622 nm. With La doping no new emission peaks were observed except for slight shift in the peak emission wavelength.