Temperature-Dependent Powder X-ray Diffraction (TD-PXRD)
Temperature-Dependent Powder X-ray Diffraction (TD-PXRD) is an analytical technique that reveals the dynamic interplay between temperature and crystallographic structure in materials. This method involves subjecting a powdered sample to incremental temperature changes while concurrently capturing X-ray diffraction patterns. By doing so, researchers can investigate the material's response to heat, offering valuable insights into phase transitions, thermal stability, and alterations in atomic arrangements. Temperature-dependent Powder X-ray Diffraction is particularly crucial in fields such as materials science, where understanding the Thermal behavior of substances is essential for tailoring their properties. This technique facilitates the exploration of phase diagrams, identification of polymorphic transformations, and characterization of materials under realistic temperature conditions, contributing to advancements in material design and manufacturing processes.
In applications ranging from pharmaceuticals to materials engineering, Temperature-Dependent Powder X-ray Diffraction proves indispensable for unraveling the intricate relationship between temperature and material structure. The insights gained from this method enable researchers to optimize manufacturing processes, design materials with specific thermal characteristics, and explore the thermal properties of both natural and synthetic compounds. Ultimately, the ability to probe temperature-dependent changes in crystallographic structure enhances our understanding of material behavior, opening avenues for innovations that impact diverse industries.
Catalyst Characterization
Temperature-dependent XRD measurements were employed to gather details about crystallite size, phase purity, and phase transition temperatures. The powder x-ray diffraction pattern of the specimen prepared at 1000°C reveals diffraction peaks characteristic of tetragonal NiCr2O4, as shown in Fig. 1 and JCPDS file no. 01-088-0109. Nevertheless, weak peaks indicative of Cr2O3 are also evident (refer to Fig. 1). As the synthesis temperature decreases, two noteworthy features emerge. Firstly, the intensity of Cr2O3 peaks increases. In the sample synthesized at 700°C, peaks characteristic of NiCr2O4 are no longer discernible, suggesting that NiCr2O4 formation commences at approximately 750°C and synthesis concludes at around 1000°C. Secondly, with decreasing synthesis temperature, in addition to the peaks characteristic of tetragonal NiCr2O4, extra peaks typical of cubic NiCr2O4 become apparent (see Fig. 1 and JCPDS file no. 01-088-0108). Figure 1b illustrates that firing at 800°C results in the simultaneous formation of both cubic and tetragonal phases. It is widely recognized that a reduction in particle size often leads to a decrease in phase transition temperature. Consequently, the concurrent presence of both phases at room temperature may be ascribed to the dispersion in crystallite size within the sample.
Reference:
Ptak M, Maczka M, Ga̧gor A, Pikul A, Macalik L, Hanuza J. Temperature-dependent XRD, IR, magnetic, SEM and TEM studies of Jahn-Teller distorted NiCr2O4 powders. J Solid State Chem 2013;201:270–9.
https://doi.org/10.1016/j.jssc.2013.03.023.
Ceramics
The successful synthesis of Pb(1-x)LaxTi(1-x)AlxO3 ceramics within the specified composition range (0≤x≤0.25) was achieved through the effective application of the sol-gel process on synthesized powders. To examine the structural transition from a tetragonal to a cubic phase, temperature-dependent X-ray diffraction (XRD) analysis was conducted. In the XRD study of the composition with x=0.09 (Fig.2a), a notable separation of two peaks (001 ) and (100) at lower temperatures was observed, indicative of a tetragonal phase. As the temperature rose, these peaks gradually fused into a singular peak at 573 K, signifying a transformation to a cubic phase (Fig. 2b). Similar temperature-dependent trends were noted for other peaks associated with the tetragonal to cubic phase transition. Furthermore, a temperature-dependent dielectric study confirmed the phase transition from a tetragonal to a cubic structure.
Reference:
Yadav AK, Verma A, Kumar S, Srihari V, Sinha AK, Reddy VR, et al. Investigation of la and Al substitution on the spontaneous polarization and lattice dynamics of the Pb(1-x)LaxTi(1-x)AlxO3 ceramics. J Appl Phys 2018;123.
https://doi.org/10.1063/1.5017765.
Material Science
Figure 3 displays the temperature dependency of the powder X-ray diffraction data. Rietveld refinements of the NdCrO3 crystal structure indicate a distorted perovskite structure akin to GdFeO3, featuring both in-phase and out-of-phase octahedral tilting distortions. Notably, the Cr–O1 distances exhibit a significant and gradual increase with temperature, while Cr–O2 distances appear to show less variation within the bounds of measurement uncertainty. The Cr–O1 bond aligns with the axis of in-phase octahedral tilting, whereas the Cr–O2 bond corresponds to out-of-phase tilting. O1 occupies a special position, while O2 occupies a general position in space group Pnma. Despite these changes, the [CrO6] octahedra maintain their undistorted form, with no observable appearance or disappearance of diffraction peaks nor any indication of anomalies in lattice parameters or unit cell volume within the 273–823 K temperature range. Therefore, the anomaly noted near 640 K does not seem related to a structural phase transition. Moreover, the transition from orthorhombic to rhombohedral symmetry observed in LaCrO3 around 529 K does not occur in NdCrO3 between room temperature and 823 K.
Reference:
Lufaso MW, Mugavero SJ, Gemmill WR, Lee Y, Vogt T, zur Loye HC. Pressure- and temperature-dependent X-ray diffraction studies of NdCrO3. J Alloys Compd 2007;433:91–6.
https://doi. org/10.1016/j.jallcom.2006.06.064.
Nanotechnology
The findings from in situ high-temperature X-ray diffraction conducted in a vacuum on ZnO nanopowder, ranging from room temperature to 700°C, are depicted in Figure 4 . ZnO nanopowder, when combined with zapon lacquer, was applied to a platinum strip functioning as a sample holder and heater for high-temperature XRD. The results indicate a reduction in XRD peak broadening as the temperature rises. The observed reflections, namely (100), (002), and (101), align with those seen in ZnO bulk, and their intensity grows with higher temperatures. As commonly known, lattice parameters exhibit temperature dependence, leading to lattice expansion with increased temperature. Notably, both particle size and lattice parameters were observed to increase with rising temperatures.
Reference:
Singh P, Kumar A, Kaushal A, Kaur D, Pandey A, Goyal RN. In-situ, high-temperature XRD studies of ZnO nanopowder prepared via cost-effective ultrasonic mist chemical vapor deposition. Bull Mater Sci 2008;31:573–7.
https: //doi.org/10.1007/s12034-008-0089-y.