The effect of low temperature annealing on the structure of Gd5Si2Ge2 alloy

Fu, Hao; Zu, Xu; He, Xiao; He, Wei; Shen, Tong

doi:10.1016/j.jallcom.2006.05.053

Cited by 5 publications

(5 citation statements)

References 11 publications

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“…Therefore it is of extreme importance to optimize sample production and thermal treatments in order to minimize the content of undesired phases, thus enhancing the amount of M structural phase. In the past few years, several works dealing with the annealing of these compounds have been presented [26,23,[28][29][30]17]. It was found that low temperature (<700 K) annealings do not promote the M phase conversion [26,30,27], but instead enhance the O(I) fraction, due to a not completely understood M → O(I) phase transformation occurring in this temperature range [31].…”

Section: Introductionmentioning

confidence: 99%

“…In the past few years, several works dealing with the annealing of these compounds have been presented [26,23,[28][29][30]17]. It was found that low temperature (<700 K) annealings do not promote the M phase conversion [26,30,27], but instead enhance the O(I) fraction, due to a not completely understood M → O(I) phase transformation occurring in this temperature range [31]. On the other hand, higher temperature annealings (>1000 K) have shown interesting results, leading to the M phase conversion, particularly for annealings at T = 1570 K [26,27].…”

Section: Introductionmentioning

confidence: 99%

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Phase control studies in Gd5Si2Ge2 giant magnetocaloric compound

Belo

Pereira

Ventura

et al. 2012

Journal of Alloys and Compounds

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a b s t r a c tA systematic set of annealings on arc-melted synthesized Gd 5 Si 2 Ge 2 sample was performed. Through powder X-ray diffraction (XRD) and magnetometry measurements we monitored the effect of varying the annealing time with constant temperature (T = 1473 K) on the formation of the monoclinic (M) crystallographic phase fraction, which is the one responsible for the giant magnetocaloric effect (GMCE) in this compound. The conversion of the orthorhombic O(I) crystallographic phase into M was achieved, resulting in a significant increase of the M mass fraction. Such conversion led to a change in the magnetic transition nature, evolving from a second to a first order transition for the as-cast and annealed samples, respectively. An optimal annealing time range for the M phase conversion was identified to be within 80-120 min at T = 1473 K followed by a rapid quenching to liquid N 2 . Furthermore, an increase up to ∼50% of the magnetocaloric effect was obtained for the sample annealed during 120 min.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Phase control studies in Gd5Si2Ge2 giant magnetocaloric compound

Belo

Pereira

Ventura

et al. 2012

Journal of Alloys and Compounds

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“…Many examples of phase transformations induced by annealing process on bulk Gd5Si2Ge2 alloys can be found in the literature [5][6][7]. In these, several phenomena are responsible for the phase transformation such as, diffusion of Si, due to higher Si content, which may favor the O(I) phase [15] and stress release by the heating process [4]. temperature at which -∆Sm is maximum was found to increase by 25%, i. e., from 193 K to 257 K.…”

Section: Methodsmentioning

confidence: 99%

“…For bulk materials, thermal treatments have been reported in the literature as a very important tool for both the minimization of secondary phases and optimization of the crystallographic phases responsible for the GMCE [4][5][6][7][8]. In fact, annealing temperatures below 700 K lead to an increase of the orthorhombic I, O(I), phase hence minimizing the MCE in Gd5Si2Ge2 [4,6]. This is, in contrast to high temperature annealing, T=1473 K, where the phase transformation was from the lower volume, O(I), to the higher volume phase, Monoclinic, M, and shown an increase in the MCE [7].…”

Section: Introductionmentioning

confidence: 99%

Annealing influence on the magnetostructural transition in Gd5Si1.3Ge2.7 thin films

et al. 2015

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Due to the emerging cooling possibilities at the micro and nanoscale, such as the fast heat exchange rate, the effort to synthesize and optimize the magnetocaloric materials at these scales is rapidly growing. Here, we report the effect of different thermal treatments on Gd5Si1.3Ge2.7 thin film in order to evaluate the correlation between the crystal structure, magnetic phase transition and magnetocaloric effect. For annealing temperatures higher than 773 K, the samples showed a typical paramagnetic behavior. On the other hand, annealing below 773 K promoted the suppression of the magnetostructural transition at 190 K, while the magnetic transition around 249 K is not affected. This magnetostructural transition extinction imparts reflected in the magnetocaloric behavior and resulted in a drastic decrease in the entropy change peak value. Nevertheless, an increase in 25% of the TC and an increasing ΔTFWHM from 23 to 49 K of its operation temperature interval, ΔT, upon annealing, are crucial for future application in magnetic refrigeration. Douro, Portugal Due to the emerging cooling possibilities at the micro and nanoscale, such as the fast heat exchange rate, the effort to synthesize and optimize the magnetocaloric materials at these scales is rapidly growing. Here, we report the effect of different thermal treatments on Gd5Si1.3Ge2.7 thin film in order to evaluate the correlation between the crystal structure, magnetic phase transition and magnetocaloric effect. For annealing temperatures higher than 500ºC, the samples showed a typical paramagnetic behavior. On the other hand, thermal treatments below 500ºC promoted the suppression of the magnetostructural transition at 190 K, while the magnetic transition around 249 K is not effected. This magnetostructural transition extinction was reflected in the magnetocaloric behavior and resulted in a drastic decrease in the entropy change peak value (of about 68%). Nevertheless, an increase in TC was reported, proving that at the nanoscale, heat treatments may be a useful tool to optimize the magnetocaloric properties in Gd5(SixGe1-x)4 thin films.

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“…[22]. Furthermore, thermal treatments and atmosphere conditions are very important in the preparation of bulk R 5 (Si,Ge) 4 compounds because these parameters control and optimize the crystallographic phase present in the samples [23,24]. In this context, this work is devoted to efforts on the ability to produce Tb 5 Si 2 Ge 2 thin films by e-beam evaporation, by changing deposition conditions as well as thermal annealing aiming to achieve of required magnetic transition responsible for the MCE.…”

Section: Introductionmentioning

confidence: 99%