Phase transition and piezoelectricity of BaZrO₃‐modified (K,Na)NbO₃ lead‐free piezoelectric thin films

Abstract

K,Na)NbO 3 (KNN) is a promising lead-free ferroelectric/piezoelectric system, to which incorporating BaZrO 3 can greatly enhance its piezoelectricity, but the mechanism is not clear. This work was conducted to investigate the phase transition in the BaZrO 3 -modifed KNN system and its contribution to piezoelectricity enhancement, using thin films with a fixed orientation and high compositional homogeneity fabricated by a sol-gel method. Two ferroelectric-to-ferroelectric phase transitions are revealed, which correspond to monoclinic M C -M A phase transition at higher temperature and rhombohedral-monoclinic M C phase transition at lower temperature. It is difficult to distinguish these phases in KNN-based bulk materials, but their differences are clear when conducting high-resolution X-ray reciprocal space mapping (RSM) on the present thin films. Piezoresponse force microscopy experiments also revealed an interesting finding that local piezoelectricity of monoclinic phases was higher than that of rhombohedral ones in KNN-based thin films. This work could shed insights on the fundamental understandings for the effect of the chemical doping, and offer guidance for property optimization in the KNN-based lead-free piezoelectrics.

Ferroelectric and dielectric properties of Ca2+-doped and Ca2+–Ti4+co-doped K0.5Na0.5NbO3thin films

“…Due to low cost and the ubiquity of Si in electronics, platinized silicon (SiPt, Pt/TiO2/SiO2/Si) is by far the most used substrate in ferroelectric oxide thin film CSD synthesis 17 . KNN thin film synthesis is no exception, and the majority of studies of KNN thin films are based on using SiPt substrates [19][20][21][22][23][24][28][29][30][31][32][33][34][35][36][40][41][42][43][46][47][48]52,53 , while a few other studies are reported using other substrates like SiO2/Si 38,58,59 , ZrO2/Si 44,45 , LaNiO3/Si 57 , Pt/MgO 39 , Pt/Al2O3 49,58 , metals 50,51,54 and SrTiO3 (STO) 18,[25][26][27]37,55,56 .…”

Analysis of the effect of annealing rate on the thinness film of BaZr0.4Ti 0.6O3 at 800°C for 2 hours

“…Sampel yang mempunyai ukuran kristal yang besar memiliki nilai FWHM yang kecil. Hasil penelian ini juga dilaporkan oleh Luo et al (2019) Tabel 1 menunjukkan ukuran kristal berbanding terbalik dengan nilai FWHM dimana laju kenaikan suhu yang kecil menyebabkan ukuran kristal membesar. Pada sudut 2θ = 22.78° nilai FWHM untuk 5°C/min sebesar 0,360° dan nilai ukuran kristal sebesar 3,94 nm, sedangkan untuk 10°C/min nilai FWHM sebesar 0,360° dan ukuran kristal 3,22 nm.…”

Electrical property and phase transition analysis of KNN-based lead-free ferroelectric films

“…With the promulgation and enforcement of relevant regulations, the usage of lead-based material is limited and the exploration on the environment friendly material is strengthened [5][6][7]. Among them, (K,Na)NbO 3 (KNN) is favored by researcher for the high Curie temperature (T C ) and excellent piezoelectric response of its ceramic form [8][9][10][11][12][13][14]. Unfortunately, due to the polymorphic phase transition (PPT) effect of the structural inhomogeneity, the electrical properties of KNN are sensitive to temperature.…”