Sintering Aid-Assisted Growth of 0.95(K0.5Na0.5)NbO3-0.05(Bi0.5Na0.5)(Zr0.85Sn0.15)O-3 Single Crystals by the Solid-State Crystal Growth Method and Their Characterization

Abstract

In this work, 0.95(K0.5Na0.5)NbO3-0.05(Bi0.5Na0.5)(Zr0.85Sn0.15)O-3 (KNN-BNZS) lead-free piezoelectric single crystals are grown by the solid-state crystal growth (SSCG) method and their phase transitions and properties characterized. Addition of an appropriate amount of Li2CO3 and Bi2O3 sintering aids considerably promotes single-crystal growth. Chemical composition of the single crystal is similar to the nominal composition with a slight deficiency in Na and K as evaluated by electron probe microanalysis (EPMA). X-Ray diffraction (XRD), electrical property measurements, and temperature-controlled Raman scattering reveal that the phase transition near room temperature is from a rhombohedral to an orthorhombic or tetragonal phase. Wide temperature range Raman scattering and dielectric properties consistently indicate transitions associated with the phase transformations or boundaries of a phase coexistence region and further details. Nontrivial frequency dependence of dielectric properties is successfully parameterized by capacitance relaxations described by Debye and Cole-Cole responses with special constant phase elements with fixed exponents of 0.5 (Warburg elements). High-frequency dielectric constants and additional dielectric relaxations and dc relaxations are deconvoluted. The modeling parameters indicate the phase transition temperatures (or boundaries of the phase coexistence region) unambiguously. Polarization-electric field and bipolar strain-electric field hysteresis loops show that the single crystal is a classic lossy ferroelectric material.