X-ray diffraction remains the most commonly utilized technique in the investigation of matter’s crystallographic structure, particularly in in-situ experiments.
Materials exposed to non-ambient conditions such as high or low temperatures may exhibit reactions or phase transitions, resulting in significant changes in the material’s crystallographic structure.
The Thermo Scientific™ ARL™ EQUINOX product line features real-time detector technology, making it ideally suited to the study of materials’ structural phase transitions at high temperatures using rapid XRD measurements.
The Anton Paar HTK16N strip heater chamber is able to accommodate experiments up to 1600 °C. When used in conjunction with the instrument’s simultaneous full pattern XRD capabilities, users are able to conduct rapid, real-time dynamic studies at high temperatures.
This article summarizes a study conducted using a Thermo Scientific™ ARL™ EQUINOX 3500 coupled to a HTK16K chamber to illustrate this setup’s capabilities.
The ARL™ EQUINOX product family features a portfolio of XRD instruments ranging from simple, user-friendly bench-top systems suited to routine analysis to sophisticated floor-standing, research-grade systems.
The Thermo Scientific™ ARL™ EQUINOX 3000/3500 instrument series floor-standing, research-grade X-ray diffractometers utilize a 3 kW high voltage generator which uses standard sealed tubes (Co, Cu or Mo).
High resolution Ge (111) monochromators and mirror optics (focal/parabolic) for high flux are also available.
The ARL™ EQUINOX 3000/3500 (Figure 1) offers much faster data collection than other diffractometers due to its unique curved position sensitive detector (CPS).
Figure 1. ARL EQUINOX 3500 diffraction system. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis
This detector is able to measure all diffraction peaks simultaneously and in real-time, making it ideally suited to in-situ measurements where it is often necessary to follow sample changes in real-time, particularly when using mirror optics (Figure 2).
Figure 2. HTK16 installed on ARL EQUINOX 3500 instrument. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis
An ARL™ EQUINOX 3500 featuring Cu Kα radiation and focal mirror optics was utilized to measure phase transitions of α-Quartz (RT – 1200 °C; 20 °C/minute; 10 seconds acquisition time) and RbNO3 (160 °C – 168 °C / 215 °C – 223 °C / 287 °C – 295 °C; 10°C/minutes; 60 seconds acquisition time).
The use of CPS detector technology enables an overview measurement in reflection of α -Quartz from room temperature to 1200 °C in less than 2 hours. The results shown in Figure 3 clearly illustrate phase transitions from α-Quartz to α-Quartz (~600 °C) and Tridymite (~1150 °C).
Figure 3. Measurement of α-Quartz from RT -1200 °C (Phase transitions indicated by white lines); zoom into (100) and (101) reflections left side. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis
It should be noted, however, that the speed of measurement has resulted in a number of deviations from literature values.
A heating program featuring a slower heating ramp is required to enable a more precise determination of the transition temperature. RbNO3 exhibits three distinct phase transitions between RT and 300 °C.
Three measurement steps with slow heating ramps of 10 °C per minute were used to determine these precise transition temperatures (Figure 4). The transition temperatures were found to be in good agreement with the literature values: 164 °C / 220 °C / 291 °C (Figure 4, white lines).
Figure 4. Measurement of RbNO3 between 160 °C and 295 °C. Image Credit: Thermo Fisher Scientific – Materials & Structural Analysis
The study summarized here illustrates the suitability of the ARL™ EQUINOX instrument line for in-situ studies. This is due to the instrument’s unique CPS real-time detection technology.
It is possible to perform measurements with high dynamics, for instance, when generating overviews or fast sample changes or the measurement of quartz. Precise measurements can be facilitated using slow heating ramps and several other steps, for example, during the measurement of RbNO3.
Produced from materials originally authored by Dr. Simon Welzmiller and Dr. Henry Pilliere from Thermo Fisher Scientific.
This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific – Materials & Structural Analysis.
For more information on this source, please visit Thermo Fisher Scientific – Materials & Structural Analysis.