Challenges in the crystal growth of Li2CuO2 and LiMnPO4

Oxygen vacancy-induced magnetic moment in edge-sharing CuO2chains of Li2CuO2−δ

“…The phase purity for the growth of Li 2 CuO 2−δ under various oxygen partial pressure (p O 2 ) has been examined using synchrotron x-ray, as shown in figure 2(a). Minor impurity phase of LiCu 2 O 2 can only be identified in the crystals grown under 100% Argon atmosphere at 7 bar pressure, which is consistent to that reported by Wizent et al on the optical floating-zone growth of Li 2 CuO 2 under 40 bar gas pressure [11]. The lattice parameters for Li 2 CuO 2 samples prepared under various oxygen partial pressures at 7 bar are summarized in table 1, where no significant oxygen partial pressure dependence is found and these refined values are in good agreement with those reported in the literature [12].…”

“…Li 2 CuO 2 melts congruently and the crystal can be pulled from the stoichiometric feed rod through stages from polycrystalline to single crystalline after the first ∼10 mm of pulling. Although lithium loss was expected for its high vapor pressure in the liquid state [11], to control the lithium and oxygen loss, mixed O 2 /(O 2 +N 2 ) gas (from 20% to 100%) of pressure up to 7 bar has been applied and reported.…”

High-pressure optical floating-zone growth of Li(Mn,Fe)PO 4 single crystals

“…For x = 0 6 and x = 1, the results agree to the melting temperatures reported in Ref. [19] and [17]. The temperature profiles in Fig.…”

Reply to Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO2 chains of Li2CuO2-δ ’

“…Spin dimerization in a singlet pair is required by the Pauli exclusion principle quantum mechanically; it is the phonon energy gain of the Peierls-like dimerization responsible for the ground state of atmosphere under 50 bar of pressure and a fast 10 mm/h pulling rate in the floating-zone growth, the oxygen vacancy must be above δ∼0.15 following our growth and characterization summary shown in table 4 of Shu 2017. The loss of oxygen in the floating-zone growth of Li CuO 2 2 has also been explored and verified by Wizent et al [11] In particular, we showed that the fully oxygenated state can be achieved only via ultrahigh pressure annealing up to 6 GPa at 800°C or a prolonged oxygen post-annealing procedure at 400°C [2]. We deduce that the INS and susceptibility data used by Kuzian and Lorenz et al must have been taken from a Li CuO 2 2 sample of significant oxygen vacancies higher than δ ∼ 0.15.…”

“…First, as shown in figure 2 (as well as figure 4 in Shu 2017), the nearly perfect linearity of 1/χ(T) in the range of ∼140-550 K implies that the temperature is high enough to be unaffected by the residue effect of the spontaneous spin exchange interaction; [6] otherwise, an upward deflection of 1/χ for  T 0 would occur as a result of the competing temperature-independent AF coupling effect. Second, the proposed * Q Qconverging temperature is unphysical and impossible to verify experimentally, as Li CuO 2 2 would suffer from severe oxygen loss, melting, or being decomposed [11], not to mention that the temperature is high enough to activate thermal electrons across the band gap, causing them to become metallic and to lose localized spins, as estimated based on the gap size of ∼0.23 eV (∼2669 K) from the thermal activation behavior of conductivity shown in the inset of figure 2 [12]. The sketched 1/χ linear line with an x-intercept of Θ∼+50 K, as proposed by Kuzian and Lorenz et al (figure 1 of Kuzian's comment) is speculative and not experimentally verifiable.…”