Unusual dielectric response in B-site size-disordered hexagonal transition metal oxides

Choudhury, Debraj; Venimadhav, Adyam; Kakarla, Chandrasekhar; Delaney, Kris T.; Devi, P. Sujatha; Mondal, P.; Nirmala, R.; Gopalakrishnan, J.; Spaldin, Nicola A.; Waghmare, Umesh V.; Sarma, D. D.
April 2010
Applied Physics Letters;4/19/2010, Vol. 96 Issue 16, p162903
Academic Journal
We discover that hexagonal holmium copper titanate (Ho2CuTiO6), has a unique and highly desirable combination of high dielectric constant, low losses, very small temperature coefficient, and low frequency dependence. Our first-principles calculations indicate that these exceptional properties result from a size-difference at the Cu/Ti B-site that suppresses the expected ferroelectric transition, combined with the dominance of intermediate-frequency polar vibrational modes in the dielectric response. Our results suggest that the use of such B-site disorder in alloys of hexagonal transition-metal oxides should generally result in similar robust dielectrics.


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