ISO/TS 5770:2025
(Main)Fine ceramics (advanced ceramics, advanced technical ceramics) — Relative method for determining thermal conductivity of ceramic coatings
Fine ceramics (advanced ceramics, advanced technical ceramics) — Relative method for determining thermal conductivity of ceramic coatings
This document specifies a test method for determination of the thermal conductivity of ceramics coatings on ceramic or metal substrate at the direction perpendicular to the surface by using relative method. Procedures for calculation, data collection, and reporting are given. This document is applicable primarily to the ceramic coatings on ceramic or metal substrates. The applicable coatings are thin ceramic coatings used as a thermal barrier coating, environmental barrier coating and wear-resistant coating. This document is applicable for coating thickness to substrate thickness ratios greater than 1/100 and less than 1/500. While this ratio range it is too low for direct measurement methods, the calculation specified in this document is effective for estimating the thermal conductivity of the coating in this range, including thermal resistance.
Céramiques techniques — Méthode indirecte pour la détermination de la conductivité thermique des revêtements céramiques
General Information
Standards Content (Sample)
Technical
Specification
ISO/TS 5770
First edition
Fine ceramics (advanced ceramics,
2025-04
advanced technical ceramics) —
Relative method for determining
thermal conductivity of ceramic
coatings
Céramiques techniques — Méthode indirecte pour la
détermination de la conductivité thermique des revêtements
céramiques
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Measurement of thermal conductivity . . 2
5.1 General .2
5.2 Measurement of thermal conductivity of substrate test pieces .3
5.3 Measurement of thermal conductivity of coated piece .3
5.4 Calculation of thermal conductivity of coatings.4
6 Analysis of measurement precision . 5
7 Test report . 6
Annex A (informative) Flash test for ceramic coatings . 7
Annex B (informative) Thermal plate method for ceramic coatings . 9
Bibliography .10
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
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iv
Technical Specification ISO/TS 5770:2025(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Relative method for determining thermal
conductivity of ceramic coatings
1 Scope
This document specifies a test method for determination of the thermal conductivity of ceramics coatings
on ceramic or metal substrate at the direction perpendicular to the surface by using relative method.
Procedures for calculation, data collection, and reporting are given.
This document is applicable primarily to the ceramic coatings on ceramic or metal substrates. The applicable
coatings are thin ceramic coatings used as a thermal barrier coating, environmental barrier coating and
wear-resistant coating. This document is applicable for coating thickness to substrate thickness ratios
greater than 1/100 and less than 1/500. While this ratio range it is too low for direct measurement methods,
the calculation specified in this document is effective for estimating the thermal conductivity of the coating
in this range, including thermal resistance.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment — Design and
metrological characteristics of micrometers for external measurements
ISO 18754, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of density and
apparent porosity
ISO 19628, Fine ceramics (advanced ceramics, advanced technical ceramics) — Thermophysical properties of
ceramic composites — Determination of specific heat capacity
ISO 18755, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of thermal
diffusivity of monolithic ceramics by flash method
ISO 19629, Fine ceramics (advanced ceramics, advanced technical ceramics) — Thermophysical properties of
ceramic composites — Determination of unidimensional thermal diffusivity by flash method
ISO 1463, Metallic and oxide coatings — Measurement of coating thickness — Microscopical method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
thermal conductivity
density of heat flow rate divided by temperature gradient under steady state condition
[SOURCE: ISO 18755:2022, 3.2]
3.2
relative method
indirect test method to determine the property of a coating by measuring the properties of a coated test
piece (composite) and an uncoated test piece (substrate), based on the theoretic relationship between the
properties of the coating, composite and substrate
3.3
interface layer
layer of material between the coating and the substrate
Note 1 to entry: It is not certain that an interface layer is present in all situations.
Note 2 to entry: The interface layer can be a transition layer artificially added before coating, or an intermediate layer
generated by the reaction between the coating and the substrate materials.
3.4
bilayer coating
sum of the interface layer and coating are considered as a bilayer coating
4 Principle
The thermal conductivity of ceramic coating (λ ) on the substrate is calculated by using the obtained thermal
c
conductivities of the composite (λ ) and substrate (λ ), under the precondition that there is no thermal
eq s
contact resistance between the coating and the substrate. If the analytical theoretic relationship among
the thermal conductivities of the coating, the substrate and the composite are determined, the thermal
conductivity of the coating can be calculated using a relational equation; then, the thermal conductivity of
the substrate and the equivalent thermal conductivity of composite are obtained.
5 Measurement of thermal conductivity
5.1 General
Thermal conductivity of a substrate and composite can be obtained by different approaches according to
the shape and size of the samples. For a fine ceramic substrate and coating, a large sample is difficult to
realize, and the values of λ and λ are often measured by the laser flash method, based on ISO 18755, or
s eq
ISO 19629 and ISO 18555 for composite substrates, combined with ISO 18754 and ISO 19628. The apparatus
for thermal diffusivity tests, dimension and shape of test pieces as well as specimen holder shall conform to
the requirements of ISO 18755. The apparatus for heat capacity tests shall conform to the requirements of
ISO 19628. The apparatus for density tests shall conform to the requirements of ISO 18754. The thicknesses
measurement shall conform to the requirements of ISO 1463.
As an example, the thermal conductivity of a ceramic coating was tested by the flash test method (See Annex
A), the experimental results are shown in Tables A.1 and A.2. The thermal conductivity of a ceramic coating
was also tested by the thermal plate method (see Annex B), the experimental results are shown in Tables B.1
and B.2.
Care needs to be taken with the preparation of the side of the test piece so that good contrast is obtained
between the coating and substrate so that good measurements of coating thickness can be obtained.
5.2 Measurement of thermal conductivity of substrate test pieces
The thermal conductivity of a homogeneous substrate test piece shall be determined by formula (1):
λα= c ρ (1)
ss ss
where
α
is the thermal diffusivity of the substrate, in m /s;
s
c
is the specific heat capacities of the substrate, in J/(kg·K);
s
ρ
is the density of the substrate, in kg/m ;
s
The measurement of thermal diffusivity of the homogeneous substrate test piece shall be in accordance
with ISO 18755, while for composite substrate shall be in accordance with ISO 19629. The measurement of
specific heat capacities of the substrate test piece shall be in accordance with ISO 19628. The measurement
of density of the substrate test piece shall be in accordance with ISO 18754.
NOTE 1 The relation between the densities of a homogeneous solid at room temperature, ρ , and at high
RT
temperature ρ has the form as below:
HT
ρ
RT
=+13αα⋅+ΔΔTT3()⋅ +⋅()α ΔT
ρ
HT
where
α
is the thermal expansion coefficient of the substrate;
ΔT
is the temperature increment.
5.3 Measurement of thermal conductivity of coated piece
The equivalent thermal conductivity of the coated piece shall be tested with the same method as the
substrate for reasonable comparison, and determined by formula (2):
λα= c ρ (2)
eq eq eq eq
where
α
is the equivalent thermal diffusivity of the coated test piece, in m /s;
eq
c
is the equivalent specific heat capacities of the coated test piece, in J/(kg·K);
eq
ρ
is the equivalent density of the coated test piece, in kg/m .
eq
The measurement of specific heat capacities of coated test piece shall be in accordance with ISO 19628. The
measurement of the density of a composite shall be in accordance with ISO 18754, and modified by NOTE 1 of 5.2.
The operation sequence of 5.2 and 5.3 can be exchanged according to the actual situation of the test pieces.
e.g., when the coated test piece is obtained, 5.3 shall be carried out first, and then grind off the coating to
measure the property of the substrate based on 5.2.
For bulk samples such as ceramic tiles and refractory materials, the values of λ and λ are often measured
s eq
by the hot-wire method given in the ISO 8894 series or the thermal plate method given in ASTM C 201.
5.4 Calculation of thermal conductivity of coatings
The thermal conductivity of ceramic coating is determined by the relative method according to the following
three
...
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