Fiantok T, Koutná N, Sangiovanni DG, Mikula M. Ceramic transition metal diboride superlattices with improved ductility and fracture toughness screened by ab initio calculations.
Sci Rep 2023;
13:12835. [PMID:
37553523 PMCID:
PMC10409783 DOI:
10.1038/s41598-023-39997-4]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 08/03/2023] [Indexed: 08/10/2023] Open
Abstract
Inherent brittleness, which easily leads to crack formation and propagation during use, is a serious problem for protective ceramic thin-film applications. Superlattice architectures, with alternating nm-thick layers of typically softer/stiffer materials, have been proven powerful method to improve the mechanical performance of, e.g., cubic transition metal nitride ceramics. Using high-throughput first-principles calculations, we propose that superlattice structures hold promise also for enhancing mechanical properties and fracture resistance of transition metal diborides with two competing hexagonal phases, [Formula: see text] and [Formula: see text]. We study 264 possible combinations of [Formula: see text], [Formula: see text] or [Formula: see text] MB[Formula: see text] (where M [Formula: see text] Al or group 3-6 transition metal) diboride superlattices. Based on energetic stability considerations, together with restrictions for lattice and shear modulus mismatch ([Formula: see text], [Formula: see text] GPa), we select 33 superlattice systems for further investigations. The identified systems are analysed in terms of mechanical stability and elastic constants, [Formula: see text], where the latter provide indication of in-plane vs. out-of-plane strength ([Formula: see text], [Formula: see text]) and ductility ([Formula: see text], [Formula: see text]). The superlattice ability to resist brittle cleavage along interfaces is estimated by Griffith's formula for fracture toughness. The [Formula: see text]-type TiB[Formula: see text]/MB[Formula: see text] (M [Formula: see text] Mo, W), HfB[Formula: see text]/WB[Formula: see text], VB[Formula: see text]/MB[Formula: see text] (M [Formula: see text] Cr, Mo), NbB[Formula: see text]/MB[Formula: see text] (M [Formula: see text] Mo, W), and [Formula: see text]-type AlB[Formula: see text]/MB[Formula: see text] (M [Formula: see text] Nb, Ta, Mo, W), are suggested as the most promising candidates providing atomic-scale basis for enhanced toughness and resistance to crack growth.
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