• M Vithal

Articles written in Bulletin of Materials Science

• A mössbauer study of hyperfine interactions in the boroferrite Fe3−xGaxBO6(x=0, 0·12)

Fe3BO6 shows no thermal hysteresis around the phase transition temperatureTSR=418 K; Fe2·88Ga0·12BO6 undergoes spin transition atTSR=403 K resulting in a reduction of theTSR. Both these features are different from the reported observations on α-Fe2O3. The two Fe3+ sites show difference in their magnetic interactions. Ga3+ replaces Fe3+ in a random manner.

• Preparation, characterization and conductivity studies of Li3–2𝑥Al2–𝑥Sb𝑥(PO4)3

New NASICON type materials of composition, Li3–2𝑥Al2–𝑥Sb𝑥(PO4)3 (𝑥 = 0.6 to 1.4), have been prepared and characterized by powder XRD and IR. D.C. conductivities were measured in the temperature range 300–573 K by a two-probe method. Impedance studies were carried out in the frequency region 102–106 Hz as a function of temperature (300–573 K). An Arrhenius behaviour is observed for all compositions by d.c. conductivity and the Cole–Cole plots obtained from impedance data do not show any spikes on the lower frequency side indicating negligible electrode effects. A maximum conductivity of 4.5 × 10-6 S cm-1 at 573 K was obtained for 𝑥 = 0.8 of the Li3–2𝑥Al2–𝑥Sb𝑥(PO4)3 system.

• Preparation and characterization studies of metaborates, Cu1–𝑥M𝑥B2O4 (M = Ni, Co and Mn; 𝑥 = 0, 0.1 and 0.5)

Copper metaborates of Cu1–𝑥M𝑥B2O4 (M = Ni, Co and Mn; 𝑥 = 0, 0.1 and 0.5) compositions are prepared using B2O3 flux. Powder XRD studies showed them all to belong to the tetragonal system with space group $I\bar{4}2$𝑑. Their infrared spectra exhibit characteristic vibrational bands of BO4 tetrahedron. The room temperature powder electron spin resonance (ESR) spectrum of copper metaborate gave a single peak at g ≈ 2.15. The diffuse reflectance spectra (DRS) of Cu1–𝑥M𝑥B2O4 (M = Ni, Co and Mn; 𝑥 = 0, 0.1 and 0.5) are consistent with ligand to metal ion charge transfer and square planar symmetry of Cu2+ ion. The ligand field parameters 𝐷𝑞xy, 𝐷s and 𝐷t are obtained.

• # Bulletin of Materials Science

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Volume 42 | Issue 6
December 2019

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