Phase transition and compressibility of LaF3 under pressures up to 40 GPa

High-pressure studies of LaH3−δ (δ=0.00, 0.15)

“…Though no measurements of electrical resistance have been performed, it might be reasonable to suggest the correlation between our highpressure observations and the detection of MI transition at lowtemperature. Alternative explanation of the observed change of the XRD pattern of nonstoichiometric might be similar to the observed structural phase transition in LaF 3 [33]. The authors suggested the orthorhombic distortion (Cmma) of the hypothetical fluoritelike structure of LaF 3 under pressure, which fits fairly well to experimental XRD patterns taken during the present investigation in the pressure region from 12.0 to 22.7 GPa (Fig.…”

“…Experimental ED-XRD pattern of LaH 2.85 taken at 22.7 GPa (open circles) and fitted to orthorhombic (Cmma) structure (solid lines) suggested in[33].…”

High-pressure and high-temperature studies on fluorite-type Pb1−xNdxF2+x (x=0.15 and 0.25)

“…The pressure-temperature experiments on such substituted samples also do not show any irreversible transformation. High-pressure experiments on tysonite-type LaF 3 are reported to have new phase formation at elevated temperature [9]. Although, the NdF 3 has similar crystal structure (tysonite) as LaF 3 , such transformation cannot be directly correlated to the present studied system, as the local polyhedra of Nd 3+ in the ␤-PbF 2 lattice, is different form that in tysonite structure.…”

“…Recently, Dyuzheva et al have reported a new orthorhombic phase of LaF 3 by application of pressure to tysonite-type LaF 3 [9]. In order to explore any possible transformation or formation of new high-density phases under high-pressure conditions, the present studies on fluorite-type solid solutions compositions in Pb 1−x Nd x F 2+x series were undertaken.…”

About the mechanism of the reconstructive structural phase transition underwent by tysonite under pressure

“…Recently, X-ray powder diffraction investigations showed that the tysonites LaF 3 and CeF 3 undergo a structural phase transition (SPT) at around 20 GPa [1,2]. In these studies, the new crystalline phase proposed was orthorhombic belonging to the space group Cmma with eight formula units in the unit cell.…”