**Acknowledgements**

used include pulsed laser ablation deposition (PLAD), DC magnetron unbalanced magnetron sputtering (DC UBMS), solid solution methods, plasma-assisted metal-organic chemical vapour

Researchers usually anneal or heat the ferroelectric samples in furnace. We have tried low temperature in rich oxygen chamber, at 200–280°C [23]. We mostly anneal our ferroelectric samples in atmospheric chamber, at various temperatures from 350 to 950°C [5, 20, 24, 28, 32, 33]. We also have varied the holding duration from 1 to 29 h [3, 7–9, 11, 17, 18, 20, 27, 29, 30, 34, 35]. The resultant ferroelectric crystal shape is either hexagonal, tetragonal, or orthorhombic [6, 9, 12, 13, 36]. To learn more about the nature of our ferroelectrics, researchers have utilised several characterisation devices. They usually start with IV meter or current-voltage photovoltaic measurement and LCR meter [3, 27, 33, 37]. They are also heavily utilising spectrophotometric devices, in an ultraviolet to visible range, visible to near-infrared range and Fourier transformed infrared (FTIR) spectrophotometry [2, 4, 10, 15, 18, 37]. To assess deep inside the ferroelectric crystal structure, researchers have utilised particle size analyser, scanning electron microscopy, atomic force microscopy, dispersive energy X-ray and X-ray diffraction device (XRD) [3, 10, 14, 16, 23]. We are currently work-

ing on an implementation of ARIMA methods to enhance FTIR and XRD results [15, 16].

With those measurement devices, researchers could observe the ferroelectric electrical characteristics such as voltage responsivity, electrical insulation/conductivity, energy gap, ellipsometric measurement, value range, accuracy level, sensitivity, hysteresis, dielectric constant, time constant and dielectric loss [2, 3, 6, 7, 10, 11, 18, 20, 36]. The researchers have also measure physical characteristics such as gravimetric calculation, depth measurement, resolution, surface roughness, structural properties and functional groups [4, 10, 23, 36]. Other than those parameters, researchers also have measured spectral and applied characteristics such as refractive index, photonic absorption, pyroelectric characteristics and solar cell efficiency [6, 9, 17, 25, 27, 30, 35].

Researchers have been developing various forms of sensors with various working principles. The sensor is a simple device, which can measure how much and produce some form of the output of mechanical, electrical and optical output. Today, developmental sensors use computing, communications and connectivity to the web, mobile smart devices and integration clouds added to the sensor capabilities [38]. The development of censorship in the healthcare world was initially widely used in hospitals, but now censorship is widely used by many patients both in public places, individual homes that support their health management. Clarke and Lyons first developed the concept of biosensing in 1962. The concept of glucose biosensor was successfully commercialised in 1975 by the instrument companies Yellow Springs and the American National Standards Institute. Currently, medical industries are massively developing the biosensor as a tool for AIDS testing and home pregnancy, allergy detection. Besides, biosensors are now widely developed for environmental applications such as detection of bacteria, pesticides and heavy metals in water samples [39]. The next sensor development is a MEMS-based sensor. This sensor has a small size accurate, and industries can integrate this sensor into the device ranging from sports hours, electronics, to cars. The U.S Government initiated an accelerated

deposition (PAMOCVD) and sol-gel method [2, 9, 14, 27, 30, 31].

4 Ferroelectrics and Their Applications

**2. Ferroelectrics material and their applications**

This work is supported by Higher Education Basic Research of Directorate General of Higher Education, Ministry of National Education, The Republic of Indonesia, contract no. 1751/ IT3.11/PN/2018 and Postgraduate Research Team of Directorate General of Higher Education, Ministry of National Education, The Republic of Indonesia, contract no. 1548/IT3.11/PN/2018
