Structure and Phase Formation Features of Ti-Zr-Ni Quasicrystalline Films under Heating

Abstract

The paper describes the growth features of thin Ti-Zr-Ni films prepared by the method of magnetron sputtering of the targets with compositions Ti53Zr30Ni18 and Ti41Zr38.3Ni20.7 on the substrates at 300 K with subsequent annealing in vacuum. The formation peculiarities of phase composition, structure and thermal stability of quasicrystalline thin films were studied. It was established that in initial state the films were X-ray-amorphous or nanocrystalline with coherence lengths (according to Scherrer) near 1.6-1.8 nm independently on the element composition of the sputtered target. This structure is relatively stable up to the temperature 673 K when the formation of the quasi-crystalline phase begins. In the films with composition of Ti53Zr30Ni18, the largest quantity of the quasicrystalline phase with a characteristic parameter aq  0.517 nm is observed at the annealing temperature of 673 K. It is added with an admixture of the 1/1 W-crystal approximant phase. In the films with Ti41Zr38.3Ni20.7 composition, an optimal annealing temperature is between 823 K and 873 K. The quasicrystalline phase is characterized by the quasicrystallinity parameter aq  0.5205 nm. Additionally, for the first time, the data on the formation of 2/1 approximant crystal as an admixture phase in this system were obtained. Under annealing at the temperatures higher than 873 K, the decomposition of the quasi-crystalline and approximant phases into crystalline phases stable at higher temperatures according to the equilibrium phase diagram was established.

Features of the Initial Stage of the Formation of Ti-Zr-Ni Quasicrystalline Thin Films

“…The film thickness ranged from 20 nm to 14.6 m. A detailed description of the method for preparing films is given in [7]. The elemental composition of the targets and films was controlled by X-ray fluorescence analysis [9].…”

“…In addition, the film-target saturated with tritium can be used as an important device of the neutron source generator based on the D-T reaction [5]. There are few works devoted to the formation of quasicrystalline coatings of the Ti-Zr-Ni system [5][6][7], in contrast to the Al-Cu-Fe system [8]. When deposited on a "cold" substrate, as a rule, the coating is always amorphous, and when deposited on a substrate heated to 500-700 C, it is difficult to maintain the required composition [5,6].…”

“…When deposited on a "cold" substrate, as a rule, the coating is always amorphous, and when deposited on a substrate heated to 500-700 C, it is difficult to maintain the required composition [5,6]. In our previous article [7], it was shown that under magnetron sputtering in a medium of purified argon at a pressure of 2•10 -1 Pa and deposition on the substrate at room temperature, the composition can be controlled; and by varying the temperature and duration of subsequent vacuum annealing, the required phase composition can be achieved. This work is devoted to the study of the initial stages of the formation of the quasicrystalline phase upon annealing of the amorphous coating.…”

BEHAVIOR OF THE Ti-Zr-Ni THIN FILM CONTAINING QUASICRYSTALLINE AND APPROXIMANT PHASES UNDER RADIATIVE-THERMAL ACTION IN TRANSITION MODES

“…A detailed characterization of the structure of the films we obtained in the initial state was given in [5]. There, the peculiarities of the formation of their structure and phase composition were discussed, and the temperature boundaries of the stability of the quasicrystalline phase in thin films were determined under vacuum annealing for 1 h. It was found that the quasicrystalline phase is formed in the temperature range of 500 to 550 C.…”

“…In the Ti-Zr-Ni system, the formation of a quasicrystalline icosahedral phase in a 100 μm thick surface layer was first observed upon pulsed irradiation of a massive Ti41.5Zr41.5Ni17 alloy with flows of hydrogen, helium, or argon with thermal loads up to 0.6 MJ/m 2 in [4]. The features of the formation of a quasicrystalline thin-film coating are described in [5,6].…”