EPR Spectra of Cr⁵⁺ Ions in KCl Crystals

Abstract

on the occasion of his 75th birthday EPR, optical, and IR absorption spectra of X-irradiated KCl crystals doped with K,CrO, and K,Cr,O, are studied. It is ascertained that the impurity enters as chromate in both cases and there are two centre typesisolated Cr0:-ions and (3-05-ions coupled with divalent cation impurities. The X-irradiation results in the formation of paramagnetic Cr0;centres with monoclinic local symmetry C,, whose excessive negative charge is compensated by an anion vacancy. The EPR spectrum due to these centres is described by a spin-Hamiltonian for S = 1/2 with g, = 1.948, gl/ = 1.953, g, = 1.967. The x-axis of the g-tensor is oriented along <001) and two other principal axes along the directions of (110) type. MCCJIeAOBaHbI CIIeHTpbI 3nP, OIITM9eCIEOrOH MH@paKpaCHOrO IIOrJIOIUeHHFI 06JIy9eHHbIX HpHCTaJIJlOB KC1 C IIpHMeCRMH K,CrO, M K&kzo7. YCTaHOBJIeHO, 9 T O B 0 6 0~~ CnysaRx npHMeCb BXOAHT B BHAe XpOMaTa, IIpHseM CyIIIeCTByXOT ABa THIIa UeHTPOB -H3OJIHpOBaH-HbIe HOHbI cl'oi-H HOHbI CrO;--, CBR3aHHble C AByXBaneHTHOfi IEaTMOHHOB IIpHMeCbIo. MOHOKJlHHHOfi JIOIEaJIbHOfi CHMMeTpHefi c,, M36bITOWIbIfi OTPHUaTeJIbHbIfi 3apFIn KOTOpbIX KOMIIeHCHpOBaH aHHOHHOfi BaKaHCHea. 06yCJIOBJIeHHbIi% MMIl CIIeKTp 3nP OIIHCbIBaeTCII CIIHH-FaMHJlbTOHHaHOM AJIR 8 = 112 C 9, = 1,948, gv = 1,953, g, = 1,967. OCb Z 9-TeH3Opa OpHeHTMpOBaHa BAOJrb ( O o l ) , a HBe HpJTHX rJlaBHbIX OCH -BAOJIb HaIIpaB-B p e 3 y m~a~e 06~1yse~nn B KpacTamax C O~D~I Q T C~ napaMarHmHbie UeHTpbI CrOl-c JIeHnii THna (110).

Probing Reversible Multielectron Transfer and Structure Evolution of Li1.2Cr0.4Mn0.4O2 Cathode Material for Li-Ion Batteries in a Voltage Range of 1.0–4.8 V

“…According to the literature, Cr 5+ only appears in a few compounds or as intermediates in some reactions involving oxidations by chromate. 68,69 For the k 3 -weighted Fourier transform of extended X-ray absorption fine structure (EXAFS) patterns in Figure 3b, the main peaks located at ∼1.5 and ∼2.4 Å are associated with metal−oxygen interaction in the first coordination shell and metal−metal interaction in the second coordination shell, respectively. During charging in Region I, the intensities of Cr oct -O and Cr-metal peaks decrease gradually, while only a slight decrease of the peak intensities of the Mn oct -O peak can be observed.…”

“…It should be pointed out that, during the charge process, no signal shows the existence of Cr 5+ . According to the literature, Cr 5+ only appears in a few compounds or as intermediates in some reactions involving oxidations by chromate. , …”