Improvement of humidity sensing performance and dielectric response through pH variation in CaCu3Ti4O12 ceramics

The internal barrier layer capacitors mechanism of CaCu3Ti4O12 (CCTO) ceramics contribute a colossal dielectric constant within it. However, the enormous dielectric loss limits its application in devices. In this work, we have improved the dielectric response of CCTO by adjusting the pH value of precursor solution during the synthesis process, followed by a relatively shorter period of sintering. The synthesized powders were characterized by XRD, FESEM, UV-Vis DRS, PL, and micro-Raman measurement techniques to study the structural, morphological, optical, and lattice vibration properties of the powder. A systemic investigation of the humidity sensing characteristics of all the samples was done at five different frequencies viz-100 Hz, 120 Hz, 1 kHz, 10 kHz, and 100 kHz. As the relative humidity (RH) changes from 33% to 95%, the dielectric constant of the CCTO based sensor increases approximately by 343%. The prepared ceramic also possesses a low dielectric loss (tan delta similar to 0.32 at 95% RH), linear response (linearity-0.988), and good stability. This report investigates the various contributing factors responsible for different humidity sensing responses and correlates them with the various experimental results obtained by characterizing the prepared samples. The significantly enhanced dielectric response at room temperature makes the pH-adjusted CCTO powder a multifunctional material for humidity sensors and energy storage devices.

Automated summary

The dielectric response of CCTO ceramics has been improved by adjusting the pH value of precursor solution and shortening the sintering time. The pH-adjusted CCTO powder shows significantly enhanced dielectric response and can be used as a multifunctional material for humidity sensors and energy storage devices at room temperature.