Tuning dielectric transitions by B′-site mixing in hybrid double perovskite crystals (CH3NH3)2[K1−xRbxCo(CN)6] (x = 0.23–0.62)

Abstract

Mixing of the B′-site alkali metals in the hybrid double perovskite crystals (CH₃NH₃)₂[K_1−xRb_xCo(CN)₆] (x = 0.23–0.62) results in a fine tuning of the phase transition temperatures and therefore the switchable dielectric constant properties. The correlations among the phase transition temperature T_c, radius of the B′-site metal ion r_B′, molar ratio x and extended tolerance factor t are established as r_B′ = (1 − x)r_K + xr_Rb, x = −13.2 + 0.645T_c^1/2, r_B′ = −32.4 + 9.02T_c^1/2 and t = 513/(14x + 616). These findings indicate the efficiency and practicability of the B′-site mixing method for tuning the phase transition-related properties of the hybrid perovskites.