Synthesis and structural and electrical investigations of a hexagonal YGdInO (0.0 ≤ x ≤ 1.0) system obtained via metastable C-type intermediates

Detailed structural and electrical investigations were carried out on an A-site disordered hexagonal YGdInO (0.0 ≤ x ≤ 1.0) series synthesized by a self-assisted gel-combustion route. The phase relations show profound temperature dependence. The metastable C-type modification could be stabilized for all the compositions, which on further heating get converted to stable hexagonal polymorphs. The conversion temperature (C-type to hexagonal) was found to increase with an increase in Y content. The system was observed to be single-phasic hexagonal at 1250 C throughout the composition range. Interestingly, the increase in planar bonds of InO polyhedra was found to be twice that of the apical bonds on Gd substitution. Careful Raman spectroscopic studies highlighted a definitive though subtle structural change from x = 0.7 onward. The same observation is also corroborated by the dielectric studies. Electric field-dependent polarization measurements showed the ferroelectric hysteresis loop for pure YInO. The system transforms from ferroelectric in YInO to almost paraelectric for GdInO. In the present study, XRD, Raman, and electrical characterizations in conjunction reveal that to tune the electrical properties of the hexagonal rare earth indates, the variation in tilting of InO polyhedra has to be influenced, which could not be brought about by isovalent A-site substitution. © 2013 American Chemical Society.