Enhancement in the dielectric and magnetic properties of Ni2+-Cu2+ co-doped BaFe11Cu1-xNixO19 hexaferrites (0.0 ≤ x ≤ 1.0)

Herein, Ni2+-Cu2+ co-doped barium hexaferrites (BaFe11Cu1-xNixO19, 0.0 ≤ x≤ 1.0 with an interval of 0.25) were successfully synthesized using a co-precipitation method. The formation of a magnetoplumbite structure with the P63/mmc space group was confirmed by Rietveld refinement of the obtained X-ray diffraction patterns. Microstructural investigations revealed grains in the shape of hexagonal plates, while co-doping resulted in a variation in the grain sizes of the prepared samples. X-ray photoelectron spectroscopy was performed to determine the valence state of iron in the prepared hexaferrites. Impedance spectroscopy analysis revealed that dielectric permittivity initially decreased with an increase in the co-dopant content up to x = 0.5 and then increased by two orders of magnitude for x = 1.0. Alternatively, resistive properties showed microstructural resistance values in the range 105-108 Ω, with the highest value obtained for the sample with x = 0.5. Furthermore, magnetic measurements indicated that all the prepared samples exhibited ferrimagnetic behaviour. Saturation magnetization and magnetic anisotropy values were found to be the highest for the sample with x = 1.0, which also had the lowest coercivity among the prepared samples. Herein, the observed variations in the obtained results can be explained by the variations in grain sizes and the Fe2+/Fe3+ ratio associated with the preferential occupation of co-dopants at octahedral sites. Based on our findings, the BaFe11Ni1O19 (x = 1.0) composition appears to be the most promising choice as a microwave absorption material among the prepared samples owing to the coexistence of high dielectric permittivity (>103 at 107 Hz) and saturation magnetization (73 emu g-1).

Fabrication of La3+ doped Ba1-x La x TiO3 ceramics with improved dielectric and ferroelectric properties using a composite-hydroxide-mediated method

Lanthanum (La³⁺) doped Ba_1-x La _x TiO₃ (x = 0.0, 0.0025, 0.005, 0.0075) ceramics were synthesized by the composite-hydroxide-mediated method. Rietveld refinement of the XRD patterns confirmed the formation of a perovskite crystal structure that transforms from tetragonal to pseudo-cubic with La³⁺ doping content (x). Scanning electron microscopy displayed a dense and homogeneous microstructure with reduced grain size on La³⁺ doping. The frequency and temperature-dependent dielectric measurements showed an improvement in the dielectric permittivity, a decrease in the ferroelectric-paraelectric transition temperature, and an increase in the dielectric diffusivity with increasing La³⁺ doping content. Complex impedance analysis indicated the semiconducting behavior with a positive temperature coefficient of resistance effect, which could be explained in terms of a charge compensation mechanism in the donor doped BaTiO₃. The ferroelectric hysteresis loops revealed that these ceramics are ferroelectric in nature, while an improvement in the energy storage density and energy storage efficiency was observed for the doped samples due to reduced grain size on La³⁺ doping. Here, the sample with x = 0.005 has a high dielectric permittivity, a low dielectric tangent loss, and the highest energy storage efficiency. This makes this composition interesting for energy storage applications.

Unusual semiconductor-metal-semiconductor transitions in magnetite Fe3O4 nanoparticles

Magnetite (Fe₃O₄) nanoparticles were successfully prepared by a co-precipitation method. Rietveld refinement on the X-ray diffraction pattern confirmed the development of a single-phase cubic spinel structure with space group Fd3̄m. However, ⁵⁷Fe Mössbauer spectroscopy suggested the presence of Fe³⁺ and Fe^2.5+ (mixed Fe³⁺ and Fe²⁺) ions at the tetrahedral and octahedral sites of the inverse spinel structure, respectively. Impedance spectroscopy measurements showed a discontinues variation in the temperature dependence of the sample's resistive behavior, indicating the appearance of semiconductor–metal–semiconductor like transitions between the temperature range of 293 and 373 K. A similar dual transition was also observed from the dielectric and conductivity measurements around the same temperature regions. The observed unusual transition is explained in term of the competitive effects among the hopping of localized/delocalized and short-range/long-range charge carriers present in the sample. Moreover, the prepared sample exhibits colossal dielectric permittivity (∼10⁶), reduced tangent loss (∼0.2) and moderate conductivity (>10⁻⁶ S cm⁻¹) values, making Fe₃O₄ nanoparticles a potential candidate for electromagnetic absorbing materials.

Herein, we report the existence of a novel semiconductor–metal–semiconductor type transition in Fe₃O₄ nanoparticles by employing impedance spectroscopy techniques.

207 An Assessment of Outcome in Patients with Anaemia (Iron Deficient and Non-Iron Deficient) Who Have Colon Cancer - Effect of Treatment with Oral/ IV Iron

Aim

Treatment of iron deficiency anaemia in patients undergoing colon cancer resection improves outcome defined by length of stay, recurrence, and requirement for blood transfusions.

Method

Retrospective analysis of patients with anaemia and colonic cancer between January 2018 - August 2019. Anaemia categorised as – Iron Deficiency Anaemia and non- Iron Deficiency anaemia. IDA was defined as hypochromic microcytic anaemia. Patient demographics, tumour location, pre- and post-operative haemoglobin, length of stay, recurrence and requirement for blood transfusions were collected plus treatment for anaemia. Comparisons made between IDA and non-IDA groups in relation to treatment for anaemia with iron (oral/IV). Non-parametric statistical tests used (median, 2-way ANOVA, Kruskal-Wallis) with significance at P <0.05.

Results

150 patients with colonic cancer identified: 77 in IDA group, 46 treated (42 oral, 4 iv iron). 11 in non- IDA group, 8 treated (oral iron).

IDA oral and IV treatment versus non-IDA:

Median age 74, 80 and 78 years (P = 0.814),

Pre- and post op Hb IDA vs non-IDA: 107, 97; 109, 101 (P 0.007 significant),

Requirement for blood transfusion (units) 0.77, 0.50;0.90 (P 0.596)

Length of Stay (days) 6, 5; 7 (P 0.113),

Tumour location: mean of right colon and transverse colon 24.33, 3.667 (P >0.1), and

Recurrence P >0.1.

Conclusions

In our series, iron treatment does not influence recurrence, length of stay, requirement for blood transfusions. Tumour location is not significantly different between IDA and non-IDA group. Patients treated with oral iron therapy are seen to have a larger drop in haemoglobin post operatively than the other groups.