Phase relations in silicon and germanium nitrides up to 98 GPa and 2400°C

Abstract

Phase relations in silicon and germanium nitrides (Si3N4 and Ge3N4) were investigated using a Kawai‐type multianvil apparatus and a laser‐heated diamond anvil cell combined with a synchrotron radiation. The pressure‐induced phase transition from the β to γ (cubic spinel‐type structure) phase was observed in both compositions. We observed the coexistence of the β and γ phases in Si3N4 at 12.4 GPa and 1800°C, while the appearance of single phase γ‐Ge3N4 was observed at pressures above 10 GPa. Our observations under higher pressures revealed that γ‐Si3N4 and γ‐Ge3N4 have wide stability fields and no postspinel transition was observed up to 98 GPa and 2400°C in both compositions. Using the room‐temperature compression curves of these materials, the bulk moduli (K0) and their pressure derivatives (K′0) were determined: K0 = 317 (16) GPa and K′0 = 6.0 (8) for γ‐Si3N4; K0 = 254 (13) GPa and K′0 = 6.0 (7) for γ‐Ge3N4.

Nitride Spinel: An Ultraincompressible High‐Pressure Form of BeP2N4

“…The powder XRD pattern of the new phase matched the Bragg reflections of the predicted spinel‐type phase (Figures and S10) . Therefore, the experimental pressure of about 47 GPa is proven sufficiently high for the phe‐BeP 2 N 4 →sp‐BeP 2 N 4 phase transition, but the minimum transition pressure may be most likely significantly lower, considering theoretical investigations on sp‐BeP 2 N 4 ( p trans =14–24 GPa) and experimental examinations of isoelectronic γ‐Si 3 N 4 ( p trans ≈13 GPa) …”

“…γ‐Si 3 N 4 has been prepared in diamond anvil cells (DAC), multianvil presses, as well as in shockwave experiments, and recently even the preparation of macroscopic transparent polycrystalline γ‐Si 3 N 4 windows has been achieved . The isothermal bulk modulus K 0 and the Vickers hardness H V of γ‐Si 3 N 4 have been determined to K 0 =290–317 GPa and H V =30–43 GPa, which makes it one of the most incompressible and hardest low‐density materials.…”

Synthesis of tin(IV) nitride with spinel structure, γ -Sn 3 N 4 , from the elements and its Raman-spectroscopic examination at high pressures

“…Nitrides of the group 14 elements having spinel structure, γ -M 3 N 4 (where M = Si, Ge or Sn), and their solid solutions [1][2][3][4][5] are promising multi-functional materials which are not only hard and stiff [6][7][8][9][10][11][12][13] but have been predicted to exhibit interesting optoelectronic properties that meet actual demands in energy consumption and functionality [14][15][16]. In particular, calculations based on the density functional theory (DFT) predicted direct band gaps for the end-members, γ -M 3 N 4 , as well as direct or nearly direct band gaps for the solid solutions γ -(Si 1−x Ge x ) 3 N 4 and γ -(Ge 1−x Sn x ) 3 N 4 [12,14,15,17].…”

Structural and Mechanical Properties of Cubic Silicon Nitride: A Molecular Dynamics Study

“…The -Si3N4 obtained to 80% percent at the shock pressure of 45 GPa and T=4000 K by using the mixtures of -Si3N4 and copper powders as initial materials [7]. In fact, the - phase transition pressures are difficult to determine in a wide temperature range [8]. Moreover, the grain size of the -Si3N4 decreases with an increase in synthesis pressure and thus the higher pressure is favorable for eliminating pores and defects along the grain boundaries, leading to enhance the mechanical properties with improvement in the hardness [4].…”