Ac response to humidity and propane of sprayed Fe-Zn oxide films

A. Avila-García, M. García-Hipólito, Y. Matsumoto-Kuwabara.

Abstract


Iron-zinc oxide films with different Zn contents were ultrasonically sprayed
on glass substrates and inter-digital gold electrodes were evaporated on
them. Films were deposited from solutions containing 2, 10 and 30 at.%
Zn. Hematite, amorphous and Franklinite structures resulted, respectively.
They were assessed as humidity and propane detectors under
alternating-current conditions for frequencies from 1 to 10$^{5}$ Hz and two
temperatures: 30 and 250$^{\circ}$C. Their impedances in dry air, humid air
and humid air plus propane were determined from voltage measurements with a
Lock-In amplifier. Sensitivity values to both humidity (53% RH.) and 189,
500 and 786 ppm of propane from the response of the real and imaginary parts
of the impedance and also the total impedance were determined as functions
of frequency. Maximum sensitivity for each case and the corresponding
frequency are reported. The maximum sensitivity to humidity ranges from
24% up to 308%. In the case of propane, the maximum sensitivity ranges
from 45% up to 711%. The largest sensitivity values correspond in all
cases to the imaginary part of the impedance. From the dynamical response,
the response and recovery times are determined, along with the
concentration-dependence of the sensitivity. The sensing mechanisms are also
discussed.

Keywords


Iron-zinc oxide films; ultrasonic spray pyrolysis; AC measurements; humidity, propane sensors

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REVISTA MEXICANA DE FÍSICA, year 67, issue 1, January-February 2021. Bimonthly Journal published by Sociedad Mexicana de Física, A. C. Departamento de Física, 2º Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Apartado Postal 70-348. Tel. (+52)55-5622-4946, https://rmf.smf.mx/ojs/rmf, e-mail: rmf@ciencias.unam.mx. Chief Editor: José Alejandro Ayala Mercado. INDAUTOR Certificate of Reserve: 04-2019-080216404400-203, ISSN: 2683-2224 (on line), 0035-001X (print), both granted by Instituto Nacional del Derecho de Autor. Responsible for the last update of this issue, Technical Staff of Sociedad Mexicana de Física, A. C., Fís. Efraín Garrido Román, 2º. Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Date of last modification, January 4, 2021.

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