ORALS

SESSION: AdvancedMaterialsWedPM2-R5	7th Intl Symposium on New & Advanced Materials and Technologies for Energy, Environment, Health and Sustainable Development
Wed. 29 Nov. 2023 / Room: Heliconia
Session Chairs: Sanjeev Khanna; Malgorzata Gradzka-Dahlke; Session Monitor: TBA

16:50: [AdvancedMaterialsWedPM211] OS
MULTI SYNTHESES METHODOLGIES OF SUPERCONDUCTING MAX PHASE TI2INN
Tetiana Prikhna¹ ; Michael Eisterer² ; Fernand Marquis³ ; Oxana Kvitniitska⁴ ; Robert Kluge⁴ ; Tetiana Serbenyuk⁵ ; Ran He⁴ ; Bernd Büchner⁴ ; Myroslav Karpets⁶ ; Viktor Moshchil⁶ ; Sebastian Gaß⁴ ; Alexander Borimskiy⁷ ; Xavier Obradors⁸ ; Teresa Puig⁸ ; ¹V. Bakul Institute NASU, Kiev, Ukraine; ²Atominstitut, Technische Universität Wien, Vienna, Austria; ³Integrated Materials Technologies and Systems (IMTS), , United States; ⁴Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany; ⁵Institute for Superhard Materials of the National Academy of Sciences of Ukraine, Kiev, Ukraine; ⁶Institute for Superhard Materials, Kiev, Ukraine; ⁷V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, Kyiv, Ukraine; ⁸Institut de Ciencia de Materials de Barcelona, CSIC, Bellaterra, Spain;
Paper Id: 375 [Abstract]

Ti2InN is the first nitride in the MAX-phase family (into Cr2AlC prototype) for which superconductivity was reported A.D. Bortolozo et al. [1]. It was proposed that the substitution of carbon in Ti2InC for nitrogen increases the superconducting transition temperature from 3.1 K to about 7.3 K due to an increase of the electronic density of states at the Fermi level (EF) from 3.67 for 4.02 states/(eV cell) [1]. The structure of Ti2InN in [1] was characterized only by X-ray. X ray pattern showed peaks of in Ti2InN and the presence of small amount of In. Unfortunately, SEM EDX or TEM studies of the synthesized material were not reported in literature. The Ti2InN samples of the study by Bortolozo et al. [1] In the present study, we prepared samples by different methods. The first two stages of synthesis followed exactly the route described in [1]. The third stage (pressure treatment) was modified. Route1: We repeated the method described in [1] but with 130 bar of nitrogen instead of argon. Route 2: Sintering in Ar in a sealed quartz ampoule. Routes 3, 7 and 8: Spark plasma sintering (SPS) at 38-50 MPa in contact with hBN. Route 4: High pressure-high temperature (HP-HT) sintering under 4 GPa in contact with hBN. Route 5: Repetition of Route 1 after removing air from the furnace more carefully. Using HP-HT, SPS methods and sintering in sealed quartz ampoule in Ar in the third stage (Routes 2, 3, 4, 7 and 8), we succeeded to synthesize Ti2InN samples containing 85.3-94 wt.% of Ti2InN (with lattice parameters a=0.3073(7)-0.3078(8) nm, c=1.4012(4)-1.4030(8) nm, unit cell volume V=114.667´10-3 - 115.114 ´10-3 nm3 ) which demonstrated superconducting behavior with Tc (onset) near 5 K. The samples prepared by SPS and HP-HT methods were highly dense. However, all samples showed a very broad magnetic transition (as susceptibility) not saturating down to 2 K. No macroscopic Meissner phase was established. The magnetization was far too weak to evidence bulk superconductivity of the entire sample (would require around 30 A/m) and hence of Ti2InN. The signal stems either from a minority phase, or from surface superconductivity. According to SEM EDX study, the stoichiometry of the Ti2InN phase of these samples were very close to 211, but in many cases a small excess of nitrogen or the presence of oxygen and even carbon (in one case) were found. We should not exclude that superconductivity in Ti2InN may be very sensitive towards non-stoichiometry (like in the case of oxygen content in YBa2Cu3O7-d , when reduction of oxygen below 6.6-6.5 atoms per one unite cell leads to disappearance of superconductivity) or toward impurities.  A pressure of 130 bar of nitrogen was not enough to suppress the decomposition of Ti2InN at 900 oC (Routes 1 and 5). The material decomposed because of In sublimation and aggregation into drops on the top of the samples (a maximum of 54 wt.% Ti2InN was observed in the materials after 10 h heating). The sample prepared by Route 1 demonstrated the best SC behavior, but the amount of Ti2InN was only 6.5 wt.%. Instead, 9 wt. % TiN, 14.5 wt. % In, 61 wt. % TiO2 and 9 wt. % In2O3 were found. The large amount of oxygen containing phases can be explained by the fact that not all air was removed from the furnace before the high nitrogen pressure was created. In the case of Route 5, when air was removed carefully, the sample decomposed as well and contained besides 54 wt.% of Ti2InN, 25 wt. % TiN, 20 wt.% In, and 1 wt.%TiO2 It seems unlikely that using nitrogen instead of argon would allow to overcome this problem (i.e. that 130 bar Ar pressure can prevent In from sublimation from Ti2InN).  All our samples contain TiN in the form of separate inclusions (with a small amount of oxygen and a very small amount of indium,). The beginning of the SC transition of all our samples was approximately 5K. The SC transition temperature of TiN was reported to be 5.3-6 K. We did not find a clear correlation between the amount of TiN and the magnetization of the materials. However, the grains of TiN phase are still a candidate for the superconducting phase in our materials. A detailed study of the Ti2InN materials structures which demonstrated Tc=7.3 K would be of great interest. Especially in view of the transition temperatures reported for g-Ti3O5 (7.1 K) and TiO (7.4 K) films.

References:
[1] A. D. Bortolozo, G. Serrano, A. Serquis, D. Rodrigues Jr., C. A. M. dos Santos, Z. Fisk, A.J.S. Machado , Solid State Commun. 150 (2010) 1364-1366. doi:10.1016/j.ssc.2010.04.036