In situ neutron powder diffraction data were collected on the high-flux medium resolution POLARIS diffractometer at ISIS, the UK spallation source at the Rutherford Appleton Laboratory, Oxfordshire, UK. A powder sample of L2P2N3 was loaded in a 4 cm high vanadium can and initial measurements were recorded at ambient temperature. Two thermocouples were attached to opposite sides of the sample container to control and monitor the furnace temperature. After calibration, diffraction data were collected at room temperature (25˚C) and 600˚C for 8 hours (150 µAmps), and every 50 degrees from 100˚C to 550˚C for 2 hours (25 µAmps) after equilibrating the temperature at each measurement. The sample was kept under a vacuum at all times. All the data were collected in the d-spacing range of 0.40 -4.50 Å and the data were corrected for absorption before analysing by Rietveld refinement.