Athermal martensitic behaviour enhanced in sodium niobate by Mn dopant and axial compression

The ferroelastic and antiferroelectric transition (between phases called P and R) in samples, pure and doped with Mn (0 - 3.3 mol%), was investigated. The phase diagram was obtained from DTA tests. The doping resulted in lowering of the P - R phase transition temperature. The shift of the P - R phase transition temperature was observed also in dielectric permittivity measured under compression. Changes in enthalpies obtained from DTA were compared to the latent heat values calculated independently from the Clapeyron - Clausius equation. Values of thermodynamic parameters of the P - R phase transition were evaluated. The EPR test showed that the Mn dopant causes disorder and local strains. Athermal martensitic behaviour of the P - R phase transition in was enhanced by applied compression and the dopant subsystem.