Polycrystalline Alkali Niobate Piezoelectric Ceramics Sintered by Microwave Technique

Abstract

Piezoelectricity or piezoelectric science remained an interesting phenomenon for some crystals since its discovery in 1880. The discovery of piezoelectric properties in polycrystalline ceramics around 1944 led to the establishment of an interesting connection between piezoelectricity and crystal symmetry analogous to the magnetic phenomenon. With the volatile nature of the widely used lead zirconate titanate (PZT) being an alarming toxic issue in the environment during processing and handling, identifying new lead-free substitutes with similar properties become an incentive for replacements of PZT ceramics. Of numerous piezoceramics, sodium–potassium niobates (KNN) have been established as promising polycrystalline candidates as potential replacements for PZTs. These materials can be processed easily using the simple double sintering conventional technique. Their properties are strongly dependent on various factors such as compositional formula, impurities/substituents, preparation method, sintering conditions like type, temperature and time, etc. The density, structural and microstructural properties that predominantly control the piezoelectric behavior are strongly dependent on the preparation process. The requirement to minimize the evaporation of constituent materials and simultaneously obtain high density, uniform microstructure, and desired crystal phase polycrystalline ceramics demands careful sintering. The chapter focuses on the sintering of certain KNN-based polycrystalline piezoceramics by different sintering techniques like conventional, microwave techniques and reports on the structural and electrical properties.