Thermochimica Acta 404 (2003) 245–249
Investigation of thermodynamic properties of Co
2
O
3
powder
Zhaodong Nan
a,∗
, Qingzhu Jiao
a
, Zhi-Cheng Tan
b
, Sun Li-Xian
b
a
Department of Chemistry, Liaoning Normal University, Dalian 116029, PR China
b
Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, PR China
Received 17 December 2002; received in revised form 14 March 2003; accepted 14 March 2003
Abstract
The isobaric molar heat capacities of powder of Co
2
O
3
were determined by an adiabatic calorimeter in the temperature range
from 78 to 350 K. No phase transition takes place in this temperature range. The relationship of C
p,m
with thermodynamic
temperature T was established as C
p,m
=-5 × 10
-6
T
3
+ 0.0026T
2
+ 0.0325T + 4.2592 (J K
-1
mol
-1
), fitting coefficient
R
2
= 0.9996. According to this relationship and the relationships between thermodynamic functions, the thermodynamic
functions of powder of Co
2
O
3
were derived with 298.15 K as reference temperature. Thermal decomposition of Co
2
O
3
powder
was studied through thermogravimetry (TG). The possible mechanism of the thermal decomposition reaction was suggested
according to the TG result.
© 2003 Elsevier Science B.V. All rights reserved.
Keywords: Heat capacity; Powder of Co
2
O
3
; Thermodynamic function; Adiabatic calorimeter; TG analysis
1. Introduction
Co
2
O
3
as additive has been applied in many fields
of material science. Co
2
O
3
may affect ceramic and
electric characteristics of ZnO varistor [1], improve
temperature-stable BaTiO
3
-based dielectrics [2], and
produce ethylene selectively in oxidative coupling of
methane as one component of catalyst [3]. Co
2
O
3
powder has been used as one of compositions of work-
ing fluid in heat pipe [4,5]. Co
2
O
3
ultrafine particle
solution has been prepared and characterized in litera-
ture [6]. The thermodynamic data of CoO and Co
3
O
4
have been reported in some handbooks [7,8]. But the
thermodynamic properties of Co
2
O
3
have not been
studied till now because of the difficult preparation of
the sample [9].
∗
Corresponding author. Tel.: +86-4258329; fax: +86-4258984.
E-mail address: zdnan65@hotmail.com (Z. Nan).
The aim of the present investigation is to gain the
thermodynamic data of powder of Co
2
O
3
by measure-
ments of the low temperature heat capacities and study
of the thermal decomposition of the sample.
2. Experimental
2.1. Experimental materials
The powder of Co
2
O
3
used for calorimetric study
was purchased from Shanghai Chemical Agent Fac-
tory, and was of spectrum grade. The average grain
size of the studied Co
2
O
3
sample was determined to
be 12 nm.
2.2. Adiabatic calorimeter
Heat-capacity measurements were carried out in
a high-precision automatic adiabatic calorimeter de-
0040-6031/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0040-6031(03)00179-5