本研究以電弧熔煉法合成 LaPd 二元金屬間化合物，並以高壓鑽石砧（Diamond Anvil Cell, DAC）結合煤油作為傳壓介質與原位氫源，透過雷射加熱誘發煤油熱裂解，於高壓條件下探索 LaPdHX之合成及其晶體結構特性。常壓粉末 X 光繞射（PXRD）與 Rietveld精修結果顯示，所合成之LaPd 為斜方晶系 Cmcm 空間群（CrB-type）結構，晶格參數與文獻報導值及第一原理計算結果高度吻合。能量色散 X 光光譜（EDS）分析確認樣品元素分布均勻，La與 Pd 之原子比例接近 1:1 化學計量比。熱重–差示掃描量熱分析（TGA/DSC）結果顯示，LaPd於約 1069°C發生相變，並於約 1113°C 熔化，展現良好之高溫熱穩定性。低溫四點探針電阻量測顯示，LaPd 於4.24 K 以上呈現典型金屬導電行為，未觀察到超導轉變。
高壓同步輻射 X 光繞射結果顯示，LaPd 在 Ne 傳壓介質中於低於 4 GPa 時維持 Cmcm 結構；相較之下，在有機傳壓介質搭配雷射加熱之條件下出現不同於初始 LaPd 之新繞射峰，顯示高壓熱解環境可能誘發新晶相形成。高壓原位及常壓顯微拉曼光譜進一步觀察到約 1620 cm⁻¹ 之 G-band 及連續螢光散射包峰，提供煤油於雷射加熱下發生熱解反應之直接光譜證據。光譜中未觀察到明顯孤立之金屬–氫振動模態，結合 X 光繞射結果，初步支持氫可能以間隙原子形式進入 LaPd 晶格，然而，碳、氧等熱解產物參與晶格改質之可能性仍無法完全排除。
綜合結構與光譜分析，本研究建立了以烷烴介質作為原位氫源，透過雷射加熱於高壓環境下誘發金屬氫化反應之實驗路徑，並取得新晶相形成及煤油熱解之初步證據。後續將透過高壓拉曼、同步輻射 X 光繞射及成分分析進一步釐清新相之化學組成與晶體結構，確認其是否對應 LaPdHX金屬氫化物，並進一步探討其潛在超導性質與高壓下之物理機制。

In this study, the binary intermetallic compound LaPd was synthesized by arc melting. A diamond anvil cell (DAC) combined with kerosene as both the pressure-transmitting medium and an in situ hydrogen source was employed to investigate the formation of LaPdHX and its crystal structural characteristics under high-pressure conditions through laser-induced pyrolysis of kerosene. Ambient-pressure powder X-ray diffraction (PXRD) and Rietveld refinement revealed that the synthesized LaPd crystallizes in the orthorhombic Cmcm space group with a CrB-type structure. Its lattice parameters are in excellent agreement with previously reported values and first-principles calculations. Energy-dispersive X-ray spectroscopy (EDS) confirmed a homogeneous elemental distribution and an La/Pd atomic ratio close to the 1:1 stoichiometric composition. Thermogravimetric analysis–differential scanning calorimetry (TGA/DSC) showed that LaPd undergoes a phase transition at approximately 1069 °C and melts at approximately 1113 °C, indicating good thermal stability at elevated temperatures. Low-temperature four-point probe measurements revealed metallic conductivity above 4.24 K, with no superconducting transition observed.
High-pressure synchrotron X-ray diffraction measurements showed that LaPd retains the Cmcm structure below 4 GPa when Ne was used as the pressure-transmitting medium. In contrast, new diffraction peaks distinct from those of pristine LaPd emerged under laser heating in organic pressure-transmitting media, suggesting that a new crystalline phase may form under high-pressure pyrolysis conditions. High-pressure in situ and ambient-pressure micro-Raman spectroscopy further revealed a G-band at approximately 1620 cm⁻¹, together with a broad continuous fluorescence background, providing direct spectroscopic evidence for the pyrolysis of kerosene induced by laser heating. No distinct isolated metal–hydrogen (M–H) vibrational modes were observed. Combined with the X-ray diffraction results, these observations tentatively support the possibility that hydrogen enters the LaPd lattice in an interstitial form. However, the participation of carbon, oxygen, or other pyrolysis products in modifying the lattice cannot be completely excluded.
Overall, the combined structural and spectroscopic results establish an experimental route for inducing metal–hydrogen reactions under high pressure using an alkane-based medium as an in situ hydrogen source and laser heating. The formation of a new crystalline phase and the pyrolysis of kerosene provide preliminary evidence for the possible synthesis of a LaPd-based hydride. Further investigations combining high-pressure Raman spectroscopy, synchrotron X-ray diffraction, and compositional analyses are required to clarify the chemical composition and crystal structure of the new phase, determine whether it corresponds to LaPdHX, and further explore its potential superconducting properties and underlying high-pressure physical mechanisms.

[1] N. W. Ashcroft, Phys. Rev. Lett. 21, 1748 (1968).
[2] N. W. Ashcroft, Phys. Rev. Lett. 92, 187002 (2004).
[3] C. Pei, S. Zhang, J. Sun, and A. List, J. Appl. Phys. 131, 070901 (2022).
[4] A. P. Drozdov, M. I. Eremets, I. A. Troyan, V. Ksenofontov, and S. I. Shylin, Nature 525, 73 (2015).
[5] E. Snider et al., Phys. Rev. Lett. 126, 117003 (2021).
[6] P. Kong et al., Nat. Commun. 12, 5075 (2021).
[7] G. de Rijk, in Proceedings of the CERN-Accelerator-School Course: Introduction to Accelerator Physics (CERN, Genève, Switzerland, 2021), arXiv:2107.03177v1 [physics.acc-ph].
[8] T. Fedotenko, L. Dubrovinsky, S. Khandarkhaeva, S. Chariton, E. Koemets, I. Koemets, M. Hanfland, and N. Dubrovinskaia, J. Alloys Compd. 844, 156179 (2020).
[9] D. Laniel et al., Nat. Commun. 13, 6987 (2022).
[10] A. C. Switendick, Phys. Status Solidi B 59, 219 (1973).
[11] P. Tripodi, D. Di Gioacchino, and J. D. Vinko, Physica C 408-410, 350 (2004).
[12] B. Guigue, G. Geneste, B. Leridon, and P. Loubeyre, J. Appl. Phys. 127, 075901 (2020).
[13] Z. M. Geballe, M. Somayazulu, N. Armanet, A. K. Mishra, M. Ahart, and R. J. Hemley, arXiv:2012.01524 (2020).
[14] M. Mito, T. Fukuyama, Y. Kitamura, H. Deguchi, K. Edalati, and Z. Horita, J. Appl. Phys. 127, 215109 (2020).
[15] M. Frost, E. E. McBride, D. Smith, J. S. Smith, and S. H. Glenzer, Adv. Mater. Interfaces 10, 2202081 (2023).
[16] A. Palenzona and S. Cirafici, J. Less-Common Met. 43, 67 (1975).
[17] T. Skośkiewicz, Phys. Status Solidi B 59, 329 (1973).
[18] A. Jain et al., APL Mater. 1, 011002 (2013); Materials Project URL: https://next-gen.materialsproject.org/materials/mp-1002115 (retrieved June 2026).
[19] N. W. Ashcroft and N. D. Mermin, Solid State Physics (Holt, Rinehart and Winston, New York, 1976).
[20] Thermal Conductivity: Theory, Properties, and Applications, edited by T. M. Tritt (Springer, New York, 2005).
[21] J. Bardeen, L. N. Cooper, and J. R. Schrieffer, Phys. Rev. 108, 1175 (1957).
[22] A. P. Hammersley, S. O. Svensson, M. Hanfland, A. N. Fitch, and D. Häusermann, High Pressure Res. 14, 235 (1996).
[23] F. London and H. London, Proc. R. Soc. London, Ser. A 149, 71 (1935).
[24] D. Zola, M. Polichetti, C. Senatore, and S. Pace, Phys. Rev. B 70, 224504 (2004).
[25] A. K. Mishra, Ph.D. dissertation, The George Washington University, 2021.
[26] H. K. Mao, J. A. Xu, and P. M. Bell, J. Geophys. Res.: Solid Earth 91, 4673 (1986).
[27] B. D. Cullity and S. R. Stock, Elements of X-ray Diffraction, 3rd ed. (Pearson, New York, 2001).
[28] 物理雙月刊編輯部, 物理雙月刊 (Bimonthly Bull. Phys. Soc. Taiwan) 43, 67bc2d33 (2021).