Luminescence detection of phase transitions

Luminescence efficiency, emission spectra and excited state lifetimes are all factors influenced by crystalline phase, pressure and temperature. Discontinuous changes in these luminescence parameters occur during phase transitions of insulating materials whilst simultaneously exciting and heating, or cooling, the samples. Radioluminescence with X-rays emphasises bulk crystal effects, whereas cathodoluminescence can be used to probe changes near to the surface. This review includes examples of new transitions, hysteresis and the value of the method for rapid surveys. Phase changes also occur for impurities and absorbates, when they exist as nanoparticles, these modify the host luminescence and reflect on crystal growth and surface treatments. Impurity effects are apparent even at the ppm level. Examples and the future potential of the method are discussed