Influence of co-modification with tungsten and tantalum on the crystal structure and electrical properties of bismuth titanate ceramics

Abstract

Bismuth titanate Bi4Ti3O12 (BIT) based lead-free piezoelectric ceramics with the formula Bi4Ti3-2xWxTaxO12 (abbreviated as BITWT-x, x = 0, 0.015, 0.03, 0.04, 0.045, 0.05) were fabricated by the conventional solid-state sintering method. The effect of W and Ta doping on the crystal structure and electrical properties of BITWT-x ceramics were investigated. BITWT-x ceramics had an orthogonal phase, and crystal structural distortion of W/Ta co-doped BITWT-x based ceramics was higher than that of BITWT-0 ceramics, which improved the ferroelectricity and the piezoelectric property. The ferroelectricity (Pr = 7.78 μC/cm2) of BITWT-0.03 ceramics was better than that (Pr = 0.84 μC/cm2) of BITWT-0 ceramics. The piezoelectric property (d33) was enhanced, and the highest d33 of BITWT-0.04 ceramics was 21.4 pC/N. Moreover, the d33 of the BITWT-x ceramics at 600 °C still kept 80% of its original d33 when the value of x was in the range of 0.03–0.045. Donor ions W6+ and Ta5+ reduced ionic conductivity (oxygen vacancies) and electron conductivity (holes), then increased the resistivity of BITWT-x ceramics (ρ400 °C = 1.82 × 108 Ω cm, x = 0.03). However, the enhanced effect reached a saturated state when x was 0.03. Thus, the BITWT-x ceramics were suitable for the high-temperature application.