Abstract
The thermal expansion and vibrational properties of [100] and [001] LaGaO3 single crystals have been studied by Thermal Mechanical Analysis and micro-Raman spectroscopy. A first order orthorhombic to rhombohedral phase transition has been confirmed by both techniques, as well as by in-situ heating using optical microscopy. The appearance of a metastable intermediate phase, tentatively assigned as monoclinic, has been detected both by optical microscopy and Raman spectroscopy upon heating of [100] and [001] LaGaO3 single crystals. Not only temperature but the stress induced orthorhombic to rhombohedral phase transition has also been detected by Raman mapping of the residual impression made by Vickers indentation. The position map of bands belonging to the lower temperature/pressure orthorhombic and the higher temperature/pressure rhombohedral phase show that the rhombohedral phase is located inside the impression, where the applied indentation stresses are the highest, and no rhombohedral phase can be located outside the impression, where the surface has not been altered by the contact stresses
