Porous Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 Ceramics for Pyroelectric Applications MOOLCHAND SHARMA, 1,5 V.P. SINGH, 2 SHATRUGHAN SINGH, 1 PUNEET AZAD, 3 BOURAOUI ILAHI, 4 and NIYAZ AHAMAD MADHAR 4 1.—IILM - College of Engineering and Technology, Greater Noida 201306, India. 2.—School of Engineering, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175005, India. 3.—Department of Electronics and Communication Engineering, Maharaja Surajmal Institute of Technology, C-4, JanakPuri, New Delhi 110058, India. 4.—Department of Physics and Astronomy, College of Sciences, King Saud University, Riyadh 11451, Kingdom of Saudi Arabia. 5.—e-mail: sharma.moolchand09@gmail.com Porous Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT) ferroelectric ceramics were fabricated using a solid-state reaction consisting of BCZT and poly(methyl methacry- late)(PMMA) (2%, 4%, 8% and 10% by wt.%) as a pore former. By increasing the PMMA content from 0% to 10%, porosity increased from 8% to 29%. It was found that the dielectric constant (e r ) decreased and the dielectric loss (tand) increased with increasing porosity. At 29% porosity, e r of the BCZT was found to decrease more, from 3481 to 1117 at 5 kHz and at room temperature. The dielectric constant and volume-specific heat capacity decreased with the in- crease in porosity which ultimately improved the pyroelectric figure-of-merits (FOMs). Further, the pyroelectric FOMs were estimated and found to be im- proved at optimum porosity. Key words: Lead-free, porous, pyroelectric, dielectric INTRODUCTION Pyroelectric materials are able to convert time- dependent thermal energy into electrical signals which have been incorporated into various devices. 1–7 Pyroelectric materials are known for their use as uncooled infrared detectors such as night vision googles. 8,9 Pyroelectric-based IR (in- frared) detectors have advantages over other IR- based technologies, e.g., high sensitivity, low power requirement, low cost and consistent performance in a wide temperature range. Thermal energy harvesting is another promising area where these materials demonstrate some advantages over See- beck effect-based thermoelectric materials. 10,11 However, both the phenomena have low conversion efficiency. These materials have also been widely investigated for their electrocaloric effect which is the conversion of electric energy into refrigeration. 12–14 Hundreds of dielectric materials have been documented in the pyroelectric fam- ily. 15,16 In order to achieve enhance the performance of pyroelectric materials, there should be a large pyroelectric coefficient, a low dielectric constant and optimum thermal properties. 17–19 These properties can be tuned using physical/chemical adjust- ments. 20–24 Composites are one of the plausible solutions for altering the above-mentioned physical properties. In this direction, porous pyroelectric ceramics can be a promising solution for thermal sensing applications. 25–28 Porous ceramics can be fabricated using volatile compounds such as carbon- based materials. 28–31 In this context, a few studies have been reported on the dielectric and pyroelectric properties of porous lead-based ceramics. 32 Thus, Zhang et al. fabricated porous pyroelectric ceramics using stearic acid. 31 The porous samples exhibited improved pyroelectric figure-of-merits (FOMs). 33,34 Few lead-free porous ceramics have been reported such as Ba 0.5 Sr 0.5 TiO 3 and Ba 0.67 Sr 0.33 TiO 3 which showed enhanced FOMs. 18,19,25,26,35 Table I reports the performance of porous pyroelectric ceramics, (Received February 10, 2018; accepted May 9, 2018) Journal of ELECTRONIC MATERIALS https://doi.org/10.1007/s11664-018-6375-6 Ó 2018 The Minerals, Metals & Materials Society