THERMISTOR Thermally Sensitive Resistor. NTC CHARACTERISTIC PRODUCT EXAMPLES APPLICATIONS

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1 ELECTRICAL CHARACTERISTICS CUFe 2 O 4 CERAMICS WITH AND WITHOUT AL 2 O 3 FOR NEGATIVE THERMAL COEFFICIENT (NTC) THERMISTOR Wiendartun 1), Dani Gustaman Syarif 2), Arief Permadi 1) 1) Department of Physics, UPI, Bandung, wien_upi@yahoo.com 2) Nuclear Technology Center for Materials and Radiometry BATAN danigusta@yahoo.com

2 INTRODUCTION THERMISTOR Thermally Sensitive Resistor. NTC CHARACTERISTIC PRODUCT EXAMPLES APPLICATIONS R vs T- THERMISTOR Current limiter thermistor Incubator Specialize Thermistor Computer

3 INTRODUCTION (Continuation) Important electronic component: Sectors: Biomedical, aerospace, instrumentation, communications, automotive and HVACR (Heating, Ventilation, Air conditioning and Refrigeration). Application : Temperature sensor, electric current limiter, flowrate meter and pressure sensor. Most, thermistors are produced from spinel ceramics transition metal oxides forming general formula AB 2 O 4. based on Predicted that the Al 2 O 3 addition can improve the characteristics of the CuFe 2 O 4. ceramic for NTC thermistors. The aim of this work is to know the effect of the Al 2 O 3 addition on the electrical characteristics, especially the electrical stability, of the CuFe 2 O 4 ceramic.

4 EXPERIMENT CuO Fe2O3 Al 2 O 3 (0;1;5mol%) Table1. Sample composition in mole %. 800 o C/2h MIXING CALCINATION CRUSHING No. CuO Fe 2 O 3 Al 2 O SIEVING 3,9 ton/cm o C/2h/air PRESSING SINTERING Heat Treatment C/ 5 / N 2 CHARACTERIZATION XRD Electrical

5 Electrical Characteristic R = R 0. Exp.(B/T) Ea = B.k α = - B/T 2 R = Thermistor resistance R 0 = Resistance at the infinite temperature B = Thermistor constant T = Temperature of thermistor Ea = Activation energy k = The Boltzmann constant α = Sensitivity of thermistor

6 RESULTS ( XRD PROFILES OF CuFe 2 O 4 BASED-CERAMICS ) XRD profile of CuFe O base-ceramic (40CuO-60Fe O ) without Al O addition. 2 4 F is peak from Fe O XRD profile of CuFe O base-ceramic (40CuO-59Fe O ) with 1 mole % Al O. 2 F is 4 peak from Fe O XRD profile of CuFe 2 O 4 base-ceramic (40CuO-55 Fe 2 O 3 ) with 5 mole % Al 2 O 3. F is peak from Fe 2 O 3.

7 RESULTS (Electrical Characteristics) Ln resist tivitas CuFe 2 O 4 + 0% Al 2 O CuFe 2 O 4 + 1% Al 2 O CuFe 2 O 4 + 5% Al 2 O /T (K -1 ) The relation between Ln Electrical Resistivity ( ρ ) and ( 1/T )

8 RESULTS (Electrical Characteristics of the ceramics ) No. Additive of Al 2 O 3 (mol %) B ( o K) (%/ o K) Market requirement for : B is 2000 o K is 2.2 %/ o K

9 RESULTS (Electrical Characteristics: Ageing Test) CuFe 2 O 4 CuFe 2 O 4 + 1% Al 2 O 3 CuFe 2 O 4 + 5% Al 2 O 3 Fitting curve error bar R (ohm) t (jam) Electrical resistance (R) as function of time (t) as the result of ageing test.

10 CONCLUSIONS All CuFe 2 O 4 structure. base-ceramic crystallized in tetragonal Thermistor constant (B) and sensitivity ( ) of the CuFe 2 O 4 base-ceramics increase with the increase of Al 2 O 3 concentration, this means that the addition of Al 2 O 3 can be used as a controlling parameter. The addition of Al 2 O 3 decreases the electrical stability of the CuFe 2 O 4 base-ceramics. Only sample without Al 2 O 3 and that added with 1 mole % Al 2 O 3 fit the electrical stability condition. Heating at 150 o C for 200 hours can be used to make CuFe 2 O 4 base-ceramic stable electrically.

11 THANK YOU ACKNOWLEGMENT The authors wish to acknowledge their deep gratitude to DIKTI, Department of National Education of Indonesian Government for financial support under Hibah PEKERTI program with contract No.014/SPP/PP/DP2M/II/April 24, 2006.

12 REFERENCES BetaTHERM Sensors [on line]. Available: E.S. Na, U.G. Paik, S.C.Choi, The effect of a sintered microstructure on the electrical properties of a Mn-Co-Ni-O thermistor, Journal of Ceramic Processing Research, Vol.2, No. 1, pp 31-34, 34, K. PARK, I.H. HAN, Effect of Al 2 O 3 addition on the microstructure and electrical properties of (Mn 0, 37 Ni 0,3 Co 0, 33 - x Al x )O 4 (0 x 0.03) NTC thermistors, Materials Science and Engineering, B119, pp , Wiendartun, D. G. Syarif, The Effect of TiO 2 Addition on the Characteristics of CuFe 2 O 4 Ceramics for NTC Thermistors, International Conference on Mathematics and Natural Sciences (ICMNS) 2006, ITB, Bandung, October 2006.