Influence of Yttrium Dopant on the Structure and Electrical Conductivity of Potassium Sodium Niobate Thin Films

Maziati Akmal Mohd Hatta,Mohd Warikh Abd Rashid,Nurul Azuwa Azmi,Mohd Asyadi Azam,Toshihiro Moriga,Umar Al-Amani Haji Azlan

doi:10.1590/1980-5373-mr-2016-0076

Maziati Akmal Mohd Hatta, Mohd Warikh Abd Rashid + Show 4 more

Open Access

https://doi.org/10.1590/1980-5373-mr-2016-0076

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Abstract

KNN thin films with diverse yttrium concentration (mol % = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) were fabricated using sol-gel spin coating technique. Doped KNN revealed that Y3+ was successfully doped into the ABO3 perovskite lattice without changing the phase formation of KNN. The thickness of the deposited layer of KNN produced with increasing dopant concentration was determined to be 200 nm with dense and well-defined grains. Afterwards, the vibrational bonding and conductivity of KNN films with diverse yttrium concentration were identified according to the charge compensation mechanism. At high dopant concentration of > 0.5 mol %, O-Nb-O bonding was asymmetric and became distorted due to B-site occupancy by yttrium dopant. Further investigation revealed that charge compensation mechanism was shifted by increasing doping concentration. As a result, yttrium-doped KNN became semi-conductive at low yttrium concentration. Meanwhile, at high concentration, yttrium-doped KNN became an insulator and underwent ionic compensation.

Highlights

A significant worldwide attention has been placed on the development and generation of novel types of piezoelectric materials such as sensors, actuators, transducers, filters and resonators
The fact that KNN is comprised of ABO3, a perovskite structure that was discovered in the 1950s was ignored through the years due to the difficulties encountered with KNN processing
Yttrium-doped KNN can revert to behave as an insulator when the donor content exceeds the critical

Summary

Introduction

A significant worldwide attention has been placed on the development and generation of novel types of piezoelectric materials such as sensors, actuators, transducers, filters and resonators. Potassium sodium niobate (K0.5 Na0.5NbO3 or KNN) has been considered as one of the ceramic materials for new lead-free piezoelectric. It exhibits high Curie temperature (420 ͦ C), high dielectric constant (~700), high remanent polarization (14μC/cm2), low coercive field (~140kV/cm) and high piezoelectric constant (~300 pC/N)[3,4,5]. This can be achieved by doping A-site ions, (K, Na)+ or B-site ion, Nb5+. Yttrium (Y3+), which is a type of rare-earth material, is known to be one of the promising dopants This is because it enhances fatigue endurance, remanent polarization and leakage current[8]. The effects of yttrium doping on the properties of KNN films are discussed

KNN films preparation

Phase determination of pure and doped KNN

Morphology of the KNN films

Vibration mode of KNN molecules

Electrical conductivity

Conclusion