Boron Solubility in Silicide Ti5Si3

Alloys of the Ti-Si-B system in the Ti5Si3 vicinity melted in an arc furnace from pure components were studied after annealing at 1850 °C for 3 h by means of XRD analysis, scanning electron microscopy with electron probe microanalysis (SEM/WDS), and 11B solid state nuclear magnetic resonance (NMR). The phase based on Ti5Si3 (D88 crystal structure of the Mn5Si3 or Hf5CuSn3 type), Ti5Si4 silicide (Sm5Ge4 crystal structure type) and TiB2 diboride were identified in the alloys. The NMR spectra contained two well-separated narrow peaks (at δ = 9 and δ = 274 ppm; Δν = 18 and Δν = 14 kHz) related to the B atoms located in the crystal lattices of TiB2 and solid solution based on Ti5Si3 respectively, which stand out against a broad peak (δ = 150 ppm, Δν = 120 kHz) from B atoms which lack for a long-range order environment. The 11B spectra were used to determine boron contents in the constituents. The B content of the Ti5Si3-based phase determined from the integral intensity of proper narrow peaks is in agreement with SEM/WDS data (both about 5 at.%).