On the matter of obtaining the composite piezoelectric thick film coatings based on phosphate binders and PZT piezo ceramics

Abstract

The possibility of producing piezoelectric composite coating based on the phosphate binder and dispersed lead zirconate-titanate based piezoelectric ceramic filler in experimentally proven in this work. Disperse filler is manufactured by sintering piezoelectric ceramics up to the density of 7.5 g/cm³ and high energy milling of sintered ceramics in planetary ball mill. Pure orthophosphoric acid and orthophosphoric acid passivated by introduction of aluminum powder were used as a phosphate binder. Pure and passivated orthophosphoric acid is added to the filler in the amount of 1, 5, 10, 15, 20 % in excess of a filler weight. Components are mixed and thinned with water to a paste consistency. Paste was applied on a stainless steel surface via screen printing, dried at room temperature, coated with graphite electrode and poled in 1 kV/mm static electric field during cooling from 100 and 290 °C (the latter being Curie temperature of a filler ceramics). After each poling cycle the values of piezoelectric modulus d₃₃, electric capacitance C₀, and dielectric loss factor tgδ were measured. Piezoelectric properties are found for coating containing 10 % of active electric phase, as coatings with lower content had insufficient mechanical strength and coatings with higher content showed no piezoelectric properties after poling. Poling under cooling from Curie temperature of a filler lead to the significant increase in d₃₃, and coating based on passivated orthophosphoric acid had double the value of d₃₃ compared to one based on pure acid. Based on obtained results mechanisms of structure and properties emergence of a piezoelectric coating in described system were proposed. Main ways to control the properties of a produced coating are noted: passivation of orthophosphoric acid, controlling the active liquid phase content and thermal treatment of produced coating. Directions of the further work to obtain piezoelectric coatings based on phosphate binders and piezoelectric ceramic fillers are proposed.