Structure, microstructure and electrical properties of new lead-free (1-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics

TL;DR

This study introduces a new lead-free piezoelectric ceramic system with a morphotropic phase boundary, demonstrating enhanced electrical properties near the boundary suitable for vibrators, transducers, and capacitors.

Contribution

It reports the synthesis and characterization of a novel (1-x)Li0.12Na0.88NbO3-xBaTiO3 system, identifying a morphotropic phase boundary and its impact on electrical properties.

Findings

Existence of a morphotropic phase boundary between orthorhombic and tetragonal phases.

Enhanced electrical properties near the MPB, including high permittivity and piezoelectric coefficients.

Potential applications in vibrators, ultrasonic transducers, and capacitors.

Abstract

A new lead-free (1-x)Li0.12Na0.88NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics have been prepared using conventional ceramics processing route. Structural analysis revealed an existence of morphotropic phase boundary (MPB), separating orthorhombic and tetragonal phases, between the BaTiO3 content, x = 10-12.5. A partial phase diagram has been established based on temperature-dependent permittivity data for this new system and a nearly vertical temperature-independent MPB is observed. An improvement in electrical properties near MPB (e.g., for x = 12.5; {\epsilon}r = 10489 at Tm, d33 = 30 pC/N, kp = 12.0 %, Qm = 162, Pr = 11.2 {\mu}C/cm2, Ec = 19.2 kV/cm, d*33 = 269 pm/V) is observed and is attributed to the ease of polarization rotation due to coexistence of orthorhombic and tetragonal phases. The results show that these materials could be suitable for piezoelectric vibrators and ultrasonic transducers applications. The sample with x = 25, also shows high dielectric permittivity, {\epsilon}r = 3060, and low dielectric loss, tan{\delta} = 0.033 which could be suitable for capacitor (X7R/Z5U) applications.