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Abstract Highly responsive, voltage‐tunable dielectrics are essential for microwave‐telecommunication electronics. Ferroelectric/relaxor materials have been leading candidates for such functionality and have exhibited agile dielectric responses. Here, it is demonstrated that relaxor materials developed from antiferroelectrics can achieve both ultrahigh dielectric response and tunability. The system, based on alloying the archetypal antiferroelectric PbZrO₃with the dielectric BaZrO₃, exhibits a more complex phase evolution than that in traditional relaxors and is characterized by an unconventional multi‐phase competition between antiferroelectric, ferroelectric, and paraelectric order. This interplay of phases can greatly enhance the local heterogeneities and results in relaxor characteristics while preserving considerable polarizability. Upon studying Pb_1‐xBa_xZrO₃forx= 0‐0.45, Pb_0.65Ba_0.35ZrO₃is found to provide for exceptional dielectric tunability under low bias fields (≈81% at 200 kV cm⁻¹and ≈91% at 500 kV cm⁻¹) at 10 kHz, outcompeting most traditional relaxor ferroelectric films. This high tunability is sustained in the radio‐frequency range, resulting in a high commutation quality factor (>2000 at 1 GHz). This work highlights the phase evolution from antiferroelectrics (with lower, “positive” dielectric tunability) to relaxors (with higher, “negative” tunability), underscoring a promising approach to develop relaxors with enhanced functional capabilities and new possibilities. 

Understanding the failure mechanisms of piezoelectric thin films is critical for the commercialization of piezoelectric microelectromechanical systems. This paper describes the failure of 0.6 mu m lead zirconate titanate (PZT) thin films on Si wafers with different in-plane stresses under large electric fields. The films failed by a combination of cracking and thermal breakdown events. It was found that the crack initiation and propagation behavior varied with the stress state of the films. The total stress required for crack initiation was estimated to be near 500 MPa. As expected, cracks propagated perpendicular to the maximum tensile stress direction. Thermal breakdown events and cracks were correlated, suggesting coupling between electrical and mechanical failure. It was also found that films that were released from the underlying substrates were less susceptible to failure by cracking. It was proposed that during electric field loading the released film stacks were able to bow and alleviate some of the stress. Released films may also experience enhanced domain wall motion that increases their fracture toughness. The results indicate that both applied stress and clamping conditions play important roles in the electromechancial failure of piezoelectric thin films.