ON INFLUENCE OF THERMAL TREATMENT ON CHARACTERISTICS OF "LEAD ZIRCONATE-TITANATE – PHOSPHATE BINDER" COMPOSITE

Abstract

The possibility to control the dielectric and piezoelectric characteristics of composite materials based on lead zirconate-titanate and phosphate binders by thermal treatment with a heating speed of no more than 100 °C per hour is proven experimentally at the present work. Two series of composite materials based on TsTS-19 (PZT-19) and different phosphate binders (orthophosphoric acid and aluminum-chromium phosphate binder) were used in preparation of “disc” type specimen according to standard OST 11 0444-87, which were untreated and thermally treated with a maximum temperature of 300 °C, 500 °C, 700 °C. Specimens were then metallized with low-temperature conductive material based on organic binder, poled in constant electric field, artificially and naturally aged. Aged specimen were investigated for density, resistivity, mechanical quality factor, dielectric loss tangent, relative dielectric permittivity, and piezoelectric modulus according to methods given in standard OST 11 0444-87. Based on the obtained results, mechanisms of interaction between lead zirconate-titanate-based piezoelectric ceramic materials and phosphate binders (unnaturalized and partially neutralized orthophosphoric acid) were proposed. It was determined that main processes occurring in investigated system under heating are direct interaction between orthophosphoric acid and ceramics, polycondensation and polymerization of a binding agent, and (at high temperatures) evaporation and condensation of lead oxide. Combination of aforementioned processes leads to achieving of the most desirable values of piezoelectric and dielectric characteristics at maximum temperatures of thermal treatment in range between 300 and 500 °C. Further optimization of the technological regimes of thermal treatment requires the use differential thermal analysis and X-ray diffraction.