Table 6.

Solubility limits for metals in metal oxides most promising for gas sensor applications.

Metal Oxide	Addition	Solubility Limit	Ref.
SnO2	In	4–10%	[263,264]
	Mn	~5–6%	[265]
	Fe; Ni; V; Mo	<5%	[241,266,267,268,269,270]
	Nb	~3%	[271]
	Co; Cr	~0.5–3%	[272,273,274]
	Cu; Al	<1%	[243,275]
	Si	1%	[276]
In2O3	Fe	~20%	[277,278]
	Ga	10–12%	[279]
	Sn	~8%	[263,280,281]
	Nb; Mo	1–3%	[282,283,284]
	Co	~1%	[285]
	Cu	<<1%	[286,287]
ZnO	Co, Mn	13–30%	[288,289]
	Fe	2–20%	[288,290]
	V	3–15%	[289,290]
	Sn	4–8%	[291]
	Cr	~6%	[290]
	Ni, Ti	~3%	[288,290]
	Al	0.3–2.0%	[292,293]
	In	<1%	[294]
	Ga	0.5%	[293]
	Cu	<0.2%	[290]

Source: data extracted from [60].