Investigation of the dielectric and piezoelectric properties of ReCa ₄O(BO₃)₃ crystals

Piezoelectric ReCa₄O(BO₃)₃ (ReCOB, Re: rare earth) crystals, including ErCOB, SmCOB, PrCOB and LaCOB, were successfully grown by the Czochralski (Cz) method. The dielectric constants were determined to be ε₁₁^T/ε₀ = 9.50, ε₂₂^T/ε₀ = 11.8 and ε₃₃^T/ε₀ =9.80 for ErCOB, ε₁₁^T/ε₀ = 9.70, ε ₂₂^T/ε₀ = 13.9 and ε₃₃ ^T/ε₀ = 9.90 for SmCOB, ε₁₁ ^T/ε₀ = 9.60, ε₂₂^T/ ε₀ = 15.3 and ε₃₃^T/ε₀ = 10.0 for PrCOB, ε₁₁^T/ε₀ = 9.40, ε₂₂^T/ε₀ = 15.0 and ε₃₃^T/ε₀ = 9.60 for LaCOB, respectively. The electromechanical coupling factors k₂₆ and piezoelectric coefficients d₂₆ were found to be 18.5% (7.6 pC N ^-1), 27.0% (12.7 pC N^-1), 31.5% (15.8 pC N^-1) and 25.0% (11.8 pC N^-1) for ErCOB, SmCOB, PrCOB and LaCOB crystals, respectively. The dielectric and piezoelectric properties as a function of Re³⁺ ion radius were studied, with maximum values being observed in the PrCOB crystals, due to the similar ion radius of Pr³⁺ and Ca ²⁺. The relationship between the structure and dielectric/ piezoelectric properties of ReCOB crystals was explored, to further optimize the dielectric and piezoelectric properties in ReCOB series crystals.