Structural phase transitions in ferroelastic RbAlF4. II. Linear birefringence investigations
- 20 January 1982
- journal article
- Published by IOP Publishing in Journal of Physics C: Solid State Physics
- Vol. 15 (2) , 197-208
- https://doi.org/10.1088/0022-3719/15/2/005
Abstract
For pt.I see ibid., vol.15, p.183 (1982). The linear birefringence (LB) of RbAlF4 is measured in the temperature range 5-630K. The discontinuous structural phase transitions (SPT) at Tcl=559.4K (P4/mmm to P4/mbm) gives rise to a small jump of the tetragonal LB of delta ( Delta nac)=6*10-7. The continuous SPT at Tc2=282.1K (P4/mbm to Pmmm) is accompanied by orthorhombic LB, Delta nab, rising from zero at Tc2 to 3.4*10-4 at T=0, whereas nac changes by about 8*10-4. The critical exponent of the order parameter obtained from Delta nab, beta =0.324, does not change on application of uniaxial stress up to 8 MPa. The deformation of the Delta nab curve due to internal strains is discussed and the switching of ferroelastic domains by uniaxial stress is demonstrated. The relationship between birefringence, spontaneous strain and the order parameter is discussed.Keywords
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