A high-temperature tensile stress study of a monolithic silicon nitride (Si3N4) was performed with time-of-flight neutron diffraction. A dedicated engineering diffractometer was employed at temperatures reaching 1375 degreesC. Rietveld refinements of diffraction spectra allowed the determination of (1) the coefficient of thermal expansion tensor during heating and (2) lattice strains during loading. The stress-strain response of individual lattice reflections was used to calculate the single-crystal elastic stiffness tensor of Si3N4 at 1375 degreesC via a self-consistent model. (C) 2003 American Institute of Physics.