Readme for Documentation of Research Datasets

Readme Creator:					Kloß, Simon D.

Readme Creation Date:				2026-04-24
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Research Dataset Title:				Structural, optical, and magnetic characterization of the rocksalt-type semiconductor Ca2TaN3 - powder diffraction, magnetization, and UV-Vis data

DOI of Publication				[to be added after acceptance]

Data Collection Location:			Ludwig-Maximilians-Universität München, Germany

Version:					1.0
Version Changes:				-

Publisher:					Kloß, Simon D.; Ludwig-Maximilians-Universität München
Publisher Identifier:				https://ror.org/05591te55
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Dataset Creator 1:				Kloß, Simon D.
Creator 1 Identifier:				0000-0002-7188-5729
Creator 1 Affiliation:				Ludwig-Maximilians-Universität München

Dataset Creator 2:				Grünwald, Adriana
Creator 2 Affiliation:				Ludwig-Maximilians-Universität München

Dataset Creator 3:				Malburg, Julian
Creator 3 Affiliation:				Ludwig-Maximilians-Universität München

Dataset Creator 4:				Werhahn, Dominik
Creator 4 Affiliation:				Ludwig-Maximilians-Universität München

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Project Name:					Preparation of rocksalt-type semiconductor Ca2TaN3 via hot isostatic pressing

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Project Description:				This dataset is part of a research project investigating the synthesis and characterization of alkaline earth transition metal nitrides (AE–M–N, AE = alkaline earth) by hot isostatic pressing (HIP). Phase diagrams of ternary AE–M–N systems remain incompletely charted, and HIP offers a route to nitride materials that are inaccessible under ambient pressure conditions through the application of high static dinitrogen pressures. Ca2TaN3 was selected as a synthetic target because its existence as a cubic solid had been mentioned in the literature but no pure preparation and full characterization had been reported.

							The project encompasses: (i) synthesis of phase-pure Ca2TaN3 by HIP; (ii) structural characterization by room-temperature powder X-ray diffraction (PXRD) and Rietveld refinement; (iii) investigation of thermal stability and thermal expansion by temperature-dependent PXRD; (iv) magnetic characterization to establish the tantalum oxidation state; and (v) optical characterization by UV-Vis diffuse reflectance spectroscopy to determine the semiconductor band gap.

							This work is funded by the DFG Emmy-Nöther Program (Project KL 3368/3-1, S. D. Kloß) and DFG Project JO257/7 (Prof. D. Johrendt, LMU Munich), which enabled use of the PPMS facility.

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Experimental Methods:				Synthesis of Ta3N5 (precursor): TaCl5 was ammonolyzed in a gas-flow tube furnace. A Ti-sponge getter placed upstream of the TaCl5 bed captured residual moisture and oxygen. The temperature was increased stepwise under flowing NH3 (ca. 2–3 gas bubbles per second): ramp at 10 °C/min to 200 °C, then 1 °C/min to 260 °C (2 h dwell), 1 °C/min to 350 °C (5 h dwell), 3 °C/min to 800 °C (3 h dwell), and cooled at 10 °C/min to room temperature.

							Synthesis of Ca2TaN3: Ca3N2 (Alfa Aesar, 99.99 %) and Ta3N5 were weighed in a molar ratio of 2.4:1, ground, and pressed into pellets inside an Ar-filled glovebox (O2, H2O < 1 ppm, MBraun). The pellets were loaded into a hot isostatic press (American Isostatic Presses Inc., Model AIP6-30H). The chamber was purged by repeated N2/vacuum cycling, then evacuated while heating to 100 °C. N2 was prefilled to 70 MPa at room temperature over 3 h. The chamber was then heated to 1400 °C over 4 h and held for 10 h at 1400 °C and 150 MPa. Heat and pressure were quenched over 1 h. All post-synthesis sample handling was performed in an inert-atmosphere glovebox owing to the high hygroscopicity of Ca2TaN3 (rapid hydrolysis in air with evolution of NH3).

							Room-temperature PXRD: Samples were packed into glass capillaries (0.5 mm outer diameter, Hilgenberg) in the glovebox, sealed, and measured on a Stoe StadiP diffractometer (Ag-Kα1 radiation, Ge(111) monochromator, MYTHEN 1K Si-strip detector) at 300 K. Rietveld refinement was performed using TOPAS Academic V6.

							Temperature-dependent PXRD: Samples were sealed in quartz capillaries (0.4 mm outer diameter, Hilgenberg) in the glovebox. Data were collected on the same Stoe StadiP equipped with a graphite furnace and an image-plate position-sensitive detector. Patterns were recorded in 20 °C steps from 60 °C to 1000 °C (heating cycle) and then in 20 °C steps from 980 °C back to 40 °C (cooling cycle). Lattice parameters at each temperature were extracted by Le Bail fitting; thermal expansion coefficients were determined by linear regression.

							Magnetic measurements: Powdered samples were sealed in polyethylene capsules of known diamagnetic contribution. Measurements were performed on a Quantum Design PPMS with VSM option. Temperature-dependent susceptibility was recorded at 30 kOe (2–300 K); field-dependent magnetization was recorded at 2 K and 300 K in fields of ±50 kOe (±5 T).

							UV-Vis spectroscopy: Diffuse reflectance spectra were recorded on a Jasco V-650 spectrophotometer (deuterium and halogen lamps, Czerny-Turner monochromator, 1200 lines/mm concave grating, photomultiplier tube detector) in the range 190–800 nm. Reflectance data were converted to the Kubelka-Munk function and analyzed as a Tauc-plot assuming a direct band gap.

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Abstract:					This dataset contains structural, optical, and magnetic characterization data for the rocksalt-type double nitride Ca2TaN3. The compound was synthesized via hot isostatic pressing (HIP) at 1400 °C and 150 MPa static dinitrogen pressure from Ca3N2 and Ta3N5, yielding a bright yellow microcrystalline powder.

						Structural Data: Room-temperature powder X-ray diffraction data were collected at 300 K on a Stoe & Cie StadiP diffractometer using Ag-Kα1 radiation. Structure solution by Rietveld refinement shows that Ca2TaN3 crystallizes in the cubic space group Fm3m (no. 225, rocksalt-type) with a lattice parameter of a = 4.7473(1) Å and a unit cell volume of V = 106.986(7) Å3. Ca and Ta statistically share a single common crystallographic position. The calculated density is 6.273 g/cm3.

						Temperature-dependent X-ray diffraction data were collected on the same diffractometer equipped with a graphite furnace and an image-plate position-sensitive detector. Measurements were performed in quartz capillaries (0.4 mm outer diameter) from 40 °C to 1000 °C (heating cycle, 20 °C steps) and back from 980 °C to 40 °C (cooling cycle, 20 °C steps). The data demonstrate excellent thermal stability of the rocksalt-type structure up to 1000 °C, with a linear thermal expansion coefficient of αa = 9.95(7) · 10−6 K−1.

						Magnetic Data: Magnetization measurements were performed using a vibration sample magnetometer (VSM) option for a Quantum Design Physical Property Measurement System (PPMS). Temperature-dependent susceptibility data were recorded at an applied field of 30 kOe (3 T) in the range 2–300 K. Field-dependent measurements were conducted at 2 K and 300 K in fields between ±50 kOe (±5 T). The data confirm a diamagnetic response consistent with tantalum in the oxidation state +V.

						UV-Vis Data: Diffuse reflectance spectra were collected on a Jasco V-650 UV/Vis spectrophotometer (190–800 nm). Analysis of the reflectance data reveals a direct optical band gap of Egap = 2.46 eV, responsible for the yellow body color of Ca2TaN3.


Keywords:					rocksalt-type nitride, Ca2TaN3, hot isostatic pressing, Rietveld refinement, powder X-ray diffraction, UV-Vis spectroscopy, band gap, magnetization, thermal expansion, alkaline earth transition metal nitride, semiconductor

Data Collection Method:				Room-temperature powder X-ray diffraction on a Stoe & Cie StadiP diffractometer (Ag-Kα1 radiation, 300 K). Temperature-dependent powder X-ray diffraction on the same instrument equipped with a graphite furnace and image-plate PSD; samples sealed in quartz capillaries (0.4 mm o.d.), measured from 40 °C to 1000 °C in 20 °C steps and cooled back to 40 °C in 20 °C steps. Magnetic characterization using a Quantum Design PPMS with VSM option (temperature-dependent measurements at 30 kOe in 2–300 K; field-dependent measurements at 2 K and 300 K, ±50 kOe). UV-Vis diffuse reflectance spectroscopy on a Jasco V-650 spectrophotometer (deuterium and halogen lamps, Czerny-Turner monochromator, 1200 lines/mm concave grating, photomultiplier tube detector), 190–800 nm.

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File List:

PXRD\
	Ca2TaN3_PXRD.xy

HTXRD\
	SKAG15c_040.xy
	SKAG15c_060.xy
	SKAG15c_080.xy
	SKAG15c_100.xy
	SKAG15c_120.xy
	SKAG15c_140.xy
	SKAG15c_160.xy
	SKAG15c_180.xy
	SKAG15c_200.xy
	SKAG15c_220.xy
	SKAG15c_240.xy
	SKAG15c_260.xy
	SKAG15c_280.xy
	SKAG15c_300.xy
	SKAG15c_320.xy
	SKAG15c_340.xy
	SKAG15c_360.xy
	SKAG15c_380.xy
	SKAG15c_400.xy
	SKAG15c_420.xy
	SKAG15c_440.xy
	SKAG15c_460.xy
	SKAG15c_480.xy
	SKAG15c_500.xy
	SKAG15c_520.xy
	SKAG15c_540.xy
	SKAG15c_560.xy
	SKAG15c_580.xy
	SKAG15c_600.xy
	SKAG15c_620.xy
	SKAG15c_640.xy
	SKAG15c_660.xy
	SKAG15c_680.xy
	SKAG15c_700.xy
	SKAG15c_720.xy
	SKAG15c_740.xy
	SKAG15c_760.xy
	SKAG15c_780.xy
	SKAG15c_800.xy
	SKAG15c_820.xy
	SKAG15c_840.xy
	SKAG15c_860.xy
	SKAG15c_880.xy
	SKAG15c_900.xy
	SKAG15c_920.xy
	SKAG15c_940.xy
	SKAG15c_960.xy
	SKAG15c_980.xy
	SKAG15c_1000.xy
	SKAG15c_040d.xy
	SKAG15c_060d.xy
	SKAG15c_080d.xy
	SKAG15c_100d.xy
	SKAG15c_120d.xy
	SKAG15c_140d.xy
	SKAG15c_160d.xy
	SKAG15c_180d.xy
	SKAG15c_200d.xy
	SKAG15c_220d.xy
	SKAG15c_240d.xy
	SKAG15c_260d.xy
	SKAG15c_280d.xy
	SKAG15c_300d.xy
	SKAG15c_320d.xy
	SKAG15c_340d.xy
	SKAG15c_360d.xy
	SKAG15c_380d.xy
	SKAG15c_400d.xy
	SKAG15c_420d.xy
	SKAG15c_440d.xy
	SKAG15c_460d.xy
	SKAG15c_480d.xy
	SKAG15c_500d.xy
	SKAG15c_520d.xy
	SKAG15c_540d.xy
	SKAG15c_560d.xy
	SKAG15c_580d.xy
	SKAG15c_600d.xy
	SKAG15c_620d.xy
	SKAG15c_640d.xy
	SKAG15c_660d.xy
	SKAG15c_680d.xy
	SKAG15c_700d.xy
	SKAG15c_720d.xy
	SKAG15c_740d.xy
	SKAG15c_760d.xy
	SKAG15c_780d.xy
	SKAG15c_800d.xy
	SKAG15c_820d.xy
	SKAG15c_840d.xy
	SKAG15c_860d.xy
	SKAG15c_880d.xy
	SKAG15c_900d.xy
	SKAG15c_920d.xy
	SKAG15c_940d.xy
	SKAG15c_960d.xy
	SKAG15c_980d.xy

Magnetisation\
	Ca2TaN3_Magnetisation_MVSH_2K_5T.DAT
	Ca2TaN3_Magnetisation_MVSH_300K_5T.DAT
	Ca2TaN3_Magnetisation_MVST_3T_2K-300K.DAT
	Ca2TaN3_Magnetisation_log.DAT
	Ca2TaN3_Magnetisation_nurStd_TT.seq
	Ca2TaN3_Magnetisation_MVSH_2K_5T.dat.gph

UVVis\
	Ca2TaN3_UVVis.txt

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File Descriptions:

PXRD\Ca2TaN3_PXRD.xy
	Room-temperature powder X-ray diffraction pattern of Ca2TaN3 collected at 300 K.
	Two-column ASCII format: column 1 = 2θ (°), column 2 = intensity (counts).
	Instrument: Stoe & Cie StadiP diffractometer, Ag-Kα1 radiation.
	Used for Rietveld structure refinement (space group Fm3m, a = 4.7473(1) Å).

HTXRD\SKAG15c_XXX.xy (heating cycle, XXX = temperature in °C)
	Temperature-dependent powder X-ray diffraction patterns collected during heating.
	Temperature range: 40–1000 °C, step size 20 °C (49 files total).
	Two-column ASCII format: column 1 = 2θ (°), column 2 = intensity (counts).
	Instrument: Stoe StadiP with graphite furnace, image-plate position-sensitive detector.
	Sample sealed in quartz capillary (0.4 mm outer diameter).

HTXRD\SKAG15c_XXXd.xy (cooling cycle, XXXd = temperature in °C)
	Temperature-dependent powder X-ray diffraction patterns collected during cooling.
	Temperature range: 980–40 °C, step size 20 °C (48 files total).
	Same format and instrument as heating cycle files.

Magnetisation\Ca2TaN3_Magnetisation_MVSH_2K_5T.DAT
	Field-dependent magnetization measurement at 2 K, applied fields ±50 kOe (±5 T).
	Native Quantum Design PPMS binary data file.
	Instrument: Quantum Design PPMS with VSM option.

Magnetisation\Ca2TaN3_Magnetisation_MVSH_300K_5T.DAT
	Field-dependent magnetization measurement at 300 K, applied fields ±50 kOe (±5 T).
	Native Quantum Design PPMS binary data file.

Magnetisation\Ca2TaN3_Magnetisation_MVST_3T_2K-300K.DAT
	Temperature-dependent magnetization measurement at 30 kOe (3 T), temperature range 2–300 K.
	Native Quantum Design PPMS binary data file.

Magnetisation\Ca2TaN3_Magnetisation_log.DAT
	Measurement log file generated by the Quantum Design PPMS MultiVu software.

Magnetisation\Ca2TaN3_Magnetisation_nurStd_TT.seq
	Measurement sequence file (script) used to run the magnetization measurements on the PPMS.

Magnetisation\Ca2TaN3_Magnetisation_MVSH_2K_5T.dat.gph
	Origin graph file (.gph) associated with the 2 K field-dependent measurement.

UVVis\Ca2TaN3_UVVis.txt
	Diffuse reflectance UV-Vis spectrum of Ca2TaN3, wavelength range 190–800 nm.
	JCAMP-DX format (JASCO); x-axis: wavelength (nm), y-axis: reflectance (%).
	Instrument: Jasco V-650 UV/Vis spectrophotometer (deuterium and halogen lamps,
	Czerny-Turner monochromator, 1200 lines/mm concave grating, photomultiplier tube detector).
	Analysis yields a direct optical band gap of Egap = 2.46 eV.

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File Formats:				.xy, .DAT, .seq, .gph, .txt

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Notes:					Funding: DFG Emmy-Nöther Program (Project KL 3368/3-1) for SDK; DFG Project JO257/7 (Prof. D. Johrendt, LMU Munich) enabling use of the PPMS.

					Ca2TaN3 is highly hygroscopic and hydrolyzes rapidly in air with evolution of ammonia. All sample handling was performed in an inert-atmosphere glovebox.

					The rocksalt-type structure of Ca2TaN3 (Fm3m, no. 225) contains Ca and Ta statistically distributed on a single cation site with N in octahedral coordination. The compound is isostructural to Mg2TaN3 but has an 8.7% larger unit cell consistent with the larger ionic radius of Ca2+ vs. Mg2+.



