Lead-free piezo-ceramic with alkaline earth doping, used e.g. to control vehicle fuel injection valve, includes perovskite- and tungsten bronze phases of specified composition

摘要

The ceramic includes at least one perovskite phase with the empirical formula Ap(Nb 1 - wTa w)O 3, where Ap is at least one alkali metal of the perovskite phase; w lies between 0 and 0.15. The ceramic also includes at least one tungsten-bronze phase with the empirical formula AwEw 2Nb 5O 1 5. Aw is at least one alkali metal of the tungsten bronze phase and Ew is at least one alkaline earth metal of the tungsten bronze. The alkali metal Ap of the perovskite phase is selected from lithium, sodium and potassium. The following relationship is satisfied: for Li xK 1-x-yNa y, x lies between 0 and 0.15, and y lies between 0.25 and 0.75. The alkaline earth metal Ew is selected from calcium, strontium and barium, the following relationship being satisfied: for Ba 1-x-ySr xCa y, x is between 0 and 1, y is between 0 and 1 and 1-x-y = 1. The tungsten bronze proportion of the tungsten bronze phase, related to the solid of the piezoceramic material, lies in the range 0.01 vol% to 25.0 vol%, especially in the range 0.05 vol% to 15.0 vol%. The proportion of lead in the piezoelectric composition is less than 0.1 mol%, preferably less than 0.01 mol%. To make a piezoelectric component, the appropriate proportions are prepared as a green body, which is then fired. The ceramic body (13) is provided with electrode layers (11, 12) of silver, copper or palladium. An independent claim IS INCLUDED FOR the method of manufacture of a piezoelectric component.