Non-stoichiometric Nb5+ Doping in KNN Ceramics for Thermal Stability
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Solution Overview
Problem
KNN-based ceramics face challenges in achieving high piezoelectric constants and temperature stability simultaneously, with poor comprehensive electrical properties and limited Curie temperature, which hinders their practical application in lead-free piezoelectric devices.
Innovation Solution
Introducing non-stoichiometric Nb5+ doping at the B-site in potassium sodium bismuth niobate tantalate zirconate ferrite ceramics, optimizing the composition to achieve enhanced piezoelectric and dielectric properties, including a high piezoelectric constant d33, Curie temperature TC, and reduced dielectric loss, through a specific preparation method involving solid phase processing and sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high piezoelectric constant d33 is achieved in KNN-based ceramics, then piezoelectric performance is improved, but Curie temperature TC decreases and temperature stability deteriorates
Solution Approach 1:
The patent applies parameter changes by introducing non-stoichiometric Nb5+ doping at the B-site with precise compositional control (x=0.01 in the formula), adjusting the chemical composition parameters to simultaneously achieve high d33 (450 pC/N) and maintain high Curie temperature (300°C), resolving the trade-off between piezoelectric performance and thermal stability
Solution Approach 2:
The patent creates a composite material system by combining multiple elements (K, Na, Bi, Nb, Ta, Zr, Fe) in a complex perovskite structure with formula (K0.45936Na0.51764Bi0.023)(Nb0.59958+0.957xTa0.05742Zr0.04Fe0.003)O3, where the synergistic interaction of different cations at A and B sites enables simultaneous optimization of piezoelectric constants and Curie temperature that cannot be achieved with single-element doping
2Manufacturing precision
If moderate or excessive amount of B-site non-stoichiometric doping is applied, then crystallinity is improved, but dielectric loss increases
Solution Approach 1:
The patent applies partial action by using a small, precise amount of non-stoichiometric Nb5+ doping (x=0.01, which corresponds to a 0.957x factor in the Nb content) rather than moderate or excessive doping. This controlled partial doping achieves sufficient crystallinity improvement through vacancy creation while avoiding the excessive dielectric loss that would result from higher doping levels
Data Source
AI summary
The present invention discloses potassium sodium bismuth niobate tantalate zirconate ferrite ceramics with non-stoichiometric Nb5+ and a preparation method therefor. A ceramic powder with a general formula of (K0.45936Na0.51764Bi0.023)(Nb0.89958+0.957xTa0.05742Zr0.04Fe0.003)O3 (−0.01≤x≤0.04) is prepared by a traditional solid phase method; and then piezoelectric ceramics are prepared by traditional electronic ceramic preparation processes such as granulating, molding, binder removal, sintering and silvering test. An excessive amount of Nb5+ doping improves the temperature stability of the ceramics by providing a domain wall pinning effect. This result demonstrates the promise of potassium sodium bismuth niobate tantalate zirconate ferrite ceramics for a wide range of applications, including sensors, actuators, and other electronic devices.