68 ISSN 0216 - 3128 Wiendartun,, dkk. Prosiding PPI - PDIPTN 2010 Pustek Akselerator dan Proses Bahan - BATAN Yogyakarta, 20 Juli 2010 SYNTHESIS AND CHARACTERIZATION OF SiO 2 ADDED- ZnFe 2 O 4 CERAMICS FOR NEGATIVE TEMPERATURE COEFFICIENT (NTC) THERMISTORS Wiendartun 1 , Dani Gustaman Syarif 2 , Fian Purmansyah 1 1) Department of Physics , UPI, Jl.Dr Setiabudhi 229 Bandung , email: wien_upi@yahoo.com 2) PTNBR BATAN, Jl.Tamansari 71 Bandung , email: danigusta@yahoo.com ABSTRACT The effect of SiO 2 addition on the characteristics of ZnFe 2 O 4 ceramics for Negative Thermal Coefficient (NTC) thermistors has been studied. The ceramics were produced by pressing a homogeneous mixture of ZnO, Fe 3 O 4 and SiO 2 (0-0.75 w/o) powders in appropriate proportions to produce ZnFe 2 O 4 based ceramics and sintering the pressed powder at 1200 o C for 2 hours in furnace air. Electrical characterization was done by measuring electrical resistivity of the sintered ceramics at various temperatures from 25 o C to 100 o C. Microstructure and structural analyses were also carried out by using Scanning Electron Microscope (SEM) and x-ray diffraction (XRD), respectively. The XRD analyses showed that the ZnFe 2 O 4 ceramics having crystal structure of cubic spinel have been well produced. The SEM images showed that SiO 2 addition made the grain size was smaller. From the electrical characteristics data, it was known that the electrical characteristics of the ZnFe 2 O 4 ceramics followed the NTC characteristic. The value of B and R RT of the produced ZnFe 2 O 4 ceramics namely B = 2928-3573 o K and ρ RT = 1616 - 6261 KΩ cm, fitted market requirement and the ZnFe 2 O 4 ceramic can be applied as NTC thermistor Key words: Ceramic , Thermistor, NTC, ZnFe 2 O 4 , SiO 2. ABSTRAK Telah dipelajari pengaruh penambahan SiO 2 terhadap karakteristik keramik ZnFe 2 O 4 untuk termistor NTC. Keramik ini dibuat dengan cara mengepres serbuk bahan campuran homogen dari ZnO, Fe 3 O 4 dan SiO 2 (0 - 0,75 % berat) dengan komposisi yang sesuai untuk menghasilkan keramik berbasis ZnFe 2 O 4 , dan menyinter serbuk hasil press pada suhu 1200 o C selama 2 jam di dalam tungku dengan atmosfir udara. .Karakterisasi sifat listrik dilakukan dengan mengukur resistivitas listriknya pada suhu yang bervariasi dimulai dari temperatur 25 o C hingga 100 o C. Analisis struktur mikro dan struktur kristal dilakukan masing- masing dengan menggunakan mikroskop elektron (SEM) dan difraktometer sinar-x (XRD). Analisis XRD memperlihatkan bahwa keramik ZnFe 2 O 4 dengan struktur kristal spinel kubik telah dapat dibuat dengan baik. Gambar-gambar SEM memperlihatkan bahwa penambahan SiO 2 . membuat ukuran butir menjadi lebih kecil. Berdasarkan data listriknya, terlihat bahwa karakteristik listrik dari keramik berbasis ZnFe 2 O 4 mengikuti karakteristik termistor NTC. Harga B dan ρ RT yang dihasilkan dari keramik ZnFe 2 O 4 yang dibuat pada penelitian ini yaitu B = 2928-3573 K dan ρ RT = 1616 - 6261 KΩ cm, memenuhi kebutuhan pasar dan dapat dipakai sebagai termistor NTC. Kata kunci : Keramik , Termistor, NTC, ZnFe 2 O 4 , SiO 2. INTRODUCTION TC thermistors are widely used in the world for many sectors of application such as biomedical, aerospace, instrumentation, communications, automotive and HVACR (Heating, Ventilation, Air conditioning and Refrigeration) [1,2]. The thermistor can be applied as temperature measurement, circuit compensation, suppression of in rush-current, flow rate sensor and pressure sensor [3]. It is well known that most NTC thermistors are produced from spinel ceramics based on transition metal oxides forming general formula AB 2 O 4 where A is metal ion in tetrahedral position and B is metal ion in octahedral position [2-10]. Many studies have been done to improve the characteristics of the spinel based-NTC thermistors [2,3,7]. This report deals with a study on the effect of SiO 2 addition on the characteristics of ZnFe 2 O 4 spinel ceramics for NTC thermistor. The ZnFe 2 O 4 ceramic has capability of being NTC thermistors, potentially, due to its semi conductive property. However, its characteristics can be still improved by addition of additive or N