Large-volume atmosphere-controlled high-temperature x-ray diffraction furnace

A new fully automated powder diffraction furnace that operates from 20 to 1600degreesC under controlled atmosphere or vacuum is reported. The diffraction furnace provides a large heated volume and stable sample positioning, thus minimizing systematic errors in the powder diffraction patterns and temperature control. The thermal expansion of alumina over the temperature range of 20-1420degreesC was used to evaluate the temperature and sample positioning errors. Analysis of 16 datasets collected over the course of 7 months, including some full-pattern Pawley refinements and Rietveld analysis, demonstrates that the thermal expansion of Al2O3 can be determined with good accuracy up to at least 1420degreesC. The specimen displacement was determined as a function of temperature using full-pattern fitting and remains well under 100 mum across the 20-1420degreesC temperature range. Heating rates of up to 1200degreesC min(-1) can be achieved without overshoot. Cooling, rates of 600degreesC min(-1) are possible at temperatures above 1300degreesC, while cooling rates of approximately 60degreesC min(-1) are possible down to similar to700degreesC. Atmosphere control is possible, and oxygen partial pressures of less than 10(-5) atm can be obtained routinely under a blanket gas.